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Initial commit — PokéSQL Game
2026-05-13 16:47:35 -07:00
{
"levels": [
{
"id": 1,
"name": "Pallet Town",
"description": "The beginning of your SQL journey",
"questions": [
{
"id": 1,
"npc": "Professor Oak",
"text": "Welcome, young trainer! Every great DBA starts here. In SQL, what command do we use to retrieve data from a table?",
"options": ["SELECT", "GET", "FETCH", "RETRIEVE"],
"answer": 0,
"explanation": "SELECT is the fundamental command for retrieving data from a SQL table. You'll use it in almost every query you write!"
},
{
"id": 2,
"npc": "Professor Oak",
"text": "Excellent! Now, if I want to see ALL columns from a table called Employees, what would I write after SELECT?",
"options": ["ALL", "EVERY", "*", "#"],
"answer": 2,
"explanation": "The asterisk (*) is a wildcard that means 'all columns'. SELECT * FROM Employees returns every column in the table."
},
{
"id": 3,
"npc": "Professor Oak",
"text": "Brilliant! After SELECT and the columns, which keyword tells SQL which table to look in?",
"options": ["IN", "FROM", "AT", "USING"],
"answer": 1,
"explanation": "FROM tells SQL which table to pull data from. A basic query looks like: SELECT * FROM TableName"
},
{
"id": 4,
"npc": "Rival Gary",
"text": "Oh, you're learning SQL too? Fine. What keyword do we use to filter rows in a query? I bet you don't know!",
"options": ["FILTER", "SEARCH", "WHERE", "LIMIT"],
"answer": 2,
"explanation": "WHERE is used to filter rows based on a condition. Example: SELECT * FROM Employees WHERE Department = 'Sales'"
},
{
"id": 5,
"npc": "Rival Gary",
"text": "Lucky guess! What operator checks if a value EQUALS something in a WHERE clause?",
"options": ["==", "=>", ":=", "="],
"answer": 3,
"explanation": "In T-SQL, a single equals sign (=) is used for equality comparison in WHERE clauses. Unlike most programming languages, SQL doesn't use ==."
},
{
"id": 6,
"npc": "Old Man Bob",
"text": "Hmm, I remember learning SQL back in my day. Do you know how to sort results from lowest to highest? That's... what order?",
"options": ["ASCENDING", "ASC", "INCREASING", "LOW"],
"answer": 1,
"explanation": "ASC (short for ASCENDING) sorts results from lowest to highest. Example: SELECT * FROM Products ORDER BY Price ASC"
},
{
"id": 7,
"npc": "Old Man Bob",
"text": "And from highest to lowest would be... DESC, right? What does DESC stand for?",
"options": ["Description", "Decrease", "Descending", "Destination"],
"answer": 2,
"explanation": "DESC stands for DESCENDING. It sorts results from highest to lowest. Example: SELECT * FROM Sales ORDER BY Amount DESC"
},
{
"id": 8,
"npc": "Nurse Joy",
"text": "Hello! When sorting, which keyword do you use before ASC or DESC?",
"options": ["SORT BY", "ORDER BY", "ARRANGE BY", "GROUP BY"],
"answer": 1,
"explanation": "ORDER BY is the keyword used to sort results. Example: SELECT * FROM Employees ORDER BY LastName ASC"
},
{
"id": 9,
"npc": "Nurse Joy",
"text": "What keyword limits how many rows are returned in T-SQL (Microsoft SQL Server)?",
"options": ["LIMIT", "ROWCOUNT", "TOP", "MAX"],
"answer": 2,
"explanation": "In T-SQL, TOP limits rows returned. Example: SELECT TOP 10 * FROM Employees. Note: MySQL uses LIMIT instead, but T-SQL uses TOP!"
},
{
"id": 10,
"npc": "Officer Jenny",
"text": "I'm checking identities here! Which SQL keyword means 'is not equal to'?",
"options": ["!=", "<>", "NOT =", "Both A and B"],
"answer": 3,
"explanation": "In T-SQL, both != and <> mean 'not equal to'. <> is the ANSI standard and older style, while != also works. Both are valid!"
},
{
"id": 11,
"npc": "Officer Jenny",
"text": "What keyword checks if a value falls within a range? For example: Price ___ 10 AND 50",
"options": ["BETWEEN", "WITHIN", "RANGE", "FROM"],
"answer": 0,
"explanation": "BETWEEN checks if a value is within a range (inclusive on both ends). Example: WHERE Price BETWEEN 10 AND 50"
},
{
"id": 12,
"npc": "Brock",
"text": "I'm a Gym Leader AND a DBA hobbyist! What keyword searches for a pattern in text data?",
"options": ["SEARCH", "FIND", "LIKE", "MATCH"],
"answer": 2,
"explanation": "LIKE is used for pattern matching. The % wildcard means 'any characters'. Example: WHERE LastName LIKE 'Sm%' finds names starting with 'Sm'."
},
{
"id": 13,
"npc": "Brock",
"text": "In a LIKE pattern, what wildcard character represents any SINGLE character?",
"options": ["%", "*", "_", "?"],
"answer": 2,
"explanation": "The underscore (_) represents exactly ONE character in a LIKE pattern. Example: WHERE Name LIKE '_ohn' matches 'John', 'Bohn', etc. % matches any number of characters."
},
{
"id": 14,
"npc": "Brock",
"text": "What keyword checks if a value is in a list? Example: WHERE Color ___ ('Red', 'Blue', 'Green')",
"options": ["CONTAINS", "WITHIN", "IN", "FROM"],
"answer": 2,
"explanation": "IN checks if a value matches any value in a list. Example: WHERE Department IN ('Sales', 'HR', 'Finance'). This is cleaner than multiple OR conditions."
},
{
"id": 15,
"npc": "Misty",
"text": "Water-type queries are my specialty! What is a NULL value in SQL?",
"options": ["Zero (0)", "An empty string", "No value / unknown", "False"],
"answer": 2,
"explanation": "NULL means the absence of any value — it's unknown or missing data. NULL is NOT zero, NOT an empty string, and NOT false. It's the complete absence of a value."
},
{
"id": 16,
"npc": "Misty",
"text": "How do you correctly check if a column IS NULL in a WHERE clause?",
"options": ["WHERE Column = NULL", "WHERE Column IS NULL", "WHERE Column == NULL", "WHERE NULL(Column)"],
"answer": 1,
"explanation": "You must use IS NULL, not = NULL. NULL cannot be compared with = because NULL is unknown. WHERE Column = NULL will never return rows!"
},
{
"id": 17,
"npc": "Misty",
"text": "And to find rows where a column has a value (is NOT empty), you use?",
"options": ["WHERE Column != NULL", "WHERE Column <> NULL", "WHERE Column IS NOT NULL", "WHERE NOT NULL(Column)"],
"answer": 2,
"explanation": "IS NOT NULL checks that a column has an actual value. Example: WHERE Email IS NOT NULL returns only rows where Email has been filled in."
},
{
"id": 18,
"npc": "Giovanni",
"text": "...You dare enter my domain? Tell me — what function counts the number of rows returned?",
"options": ["TOTAL()", "SUM()", "COUNT()", "NUMBER()"],
"answer": 2,
"explanation": "COUNT() counts rows. COUNT(*) counts all rows including NULLs. COUNT(ColumnName) counts only non-NULL values in that column."
},
{
"id": 19,
"npc": "Giovanni",
"text": "What function returns the total SUM of numeric values in a column?",
"options": ["TOTAL()", "ADD()", "SUM()", "CALC()"],
"answer": 2,
"explanation": "SUM() adds up all values in a numeric column. Example: SELECT SUM(Salary) FROM Employees returns the total payroll."
},
{
"id": 20,
"npc": "Giovanni",
"text": "What function returns the AVERAGE value of a numeric column?",
"options": ["MEAN()", "AVG()", "MID()", "AVERAGE()"],
"answer": 1,
"explanation": "AVG() calculates the average. Example: SELECT AVG(Salary) FROM Employees. AVG ignores NULL values automatically."
},
{
"id": 21,
"npc": "Team Rocket Grunt",
"text": "Prepare for trouble! What function returns the largest value in a column?",
"options": ["HIGHEST()", "TOP()", "MAX()", "LARGEST()"],
"answer": 2,
"explanation": "MAX() returns the maximum value. Works on numbers, dates, and text. Example: SELECT MAX(Salary) FROM Employees"
},
{
"id": 22,
"npc": "Team Rocket Grunt",
"text": "Make it double! What function returns the SMALLEST value?",
"options": ["LOWEST()", "BOTTOM()", "MIN()", "FIRST()"],
"answer": 2,
"explanation": "MIN() returns the minimum value. Example: SELECT MIN(HireDate) FROM Employees returns the earliest hire date."
},
{
"id": 23,
"npc": "Scientist Bill",
"text": "I've been studying GROUP BY! What does GROUP BY do in a query?",
"options": ["Sorts results", "Groups rows with same values for aggregate functions", "Joins tables together", "Filters results"],
"answer": 1,
"explanation": "GROUP BY groups rows that have the same values in specified columns, allowing aggregate functions (COUNT, SUM, AVG) to be applied to each group."
},
{
"id": 24,
"npc": "Scientist Bill",
"text": "When using GROUP BY, what keyword filters GROUPS (not individual rows)?",
"options": ["WHERE", "FILTER", "HAVING", "GROUPWHERE"],
"answer": 2,
"explanation": "HAVING filters groups after GROUP BY. WHERE filters rows BEFORE grouping. Example: SELECT Dept, COUNT(*) FROM Employees GROUP BY Dept HAVING COUNT(*) > 5"
},
{
"id": 25,
"npc": "Scientist Bill",
"text": "What is the correct ORDER of these SQL clauses? SELECT, FROM, WHERE, GROUP BY, HAVING, ORDER BY",
"options": [
"SELECT, FROM, WHERE, GROUP BY, HAVING, ORDER BY",
"FROM, SELECT, WHERE, GROUP BY, HAVING, ORDER BY",
"SELECT, WHERE, FROM, GROUP BY, HAVING, ORDER BY",
"SELECT, FROM, GROUP BY, WHERE, HAVING, ORDER BY"
],
"answer": 0,
"explanation": "The correct SQL clause order is: SELECT → FROM → WHERE → GROUP BY → HAVING → ORDER BY. Think of it as: what, from where, filtered how, grouped by, group filtered by, sorted by."
},
{
"id": 26,
"npc": "Fisherman Ralph",
"text": "I catch data like fish! What is an ALIAS in SQL?",
"options": ["A table backup", "A temporary name for a column or table", "A type of JOIN", "A stored procedure"],
"answer": 1,
"explanation": "An alias gives a column or table a temporary name in your query. Example: SELECT FirstName AS 'First Name' FROM Employees. The AS keyword is optional but makes it readable."
},
{
"id": 27,
"npc": "Fisherman Ralph",
"text": "What keyword is used to create an alias for a column?",
"options": ["NAMED", "CALLED", "AS", "ALIAS"],
"answer": 2,
"explanation": "AS creates an alias. Example: SELECT COUNT(*) AS TotalEmployees FROM Employees. You can also omit AS: SELECT COUNT(*) TotalEmployees — both work in T-SQL."
},
{
"id": 28,
"npc": "Hiker Taro",
"text": "Climbing data mountains! What does DISTINCT do in a SELECT query?",
"options": ["Sorts results alphabetically", "Removes duplicate rows from results", "Selects only NULL values", "Limits to 1 row"],
"answer": 1,
"explanation": "DISTINCT removes duplicate rows. Example: SELECT DISTINCT Department FROM Employees returns each department name only once, even if many employees share a department."
},
{
"id": 29,
"npc": "Hiker Taro",
"text": "What is the purpose of a JOIN in SQL?",
"options": ["To delete rows", "To combine rows from two or more tables based on a related column", "To group data together", "To sort multiple columns"],
"answer": 1,
"explanation": "JOIN combines rows from two or more tables based on a related column (usually a key). This is how relational databases link related data together."
},
{
"id": 30,
"npc": "Hiker Taro",
"text": "What type of JOIN returns only rows where there is a MATCH in BOTH tables?",
"options": ["LEFT JOIN", "RIGHT JOIN", "FULL JOIN", "INNER JOIN"],
"answer": 3,
"explanation": "INNER JOIN (or just JOIN) returns only rows where the join condition matches in BOTH tables. Rows with no match on either side are excluded."
},
{
"id": 31,
"npc": "Gym Leader Surge",
"text": "SHOCKING! What does a LEFT JOIN return?",
"options": [
"Only rows with matches in both tables",
"All rows from the LEFT table, plus matching rows from the right (NULLs if no match)",
"All rows from the RIGHT table only",
"All rows from both tables"
],
"answer": 1,
"explanation": "LEFT JOIN returns ALL rows from the left table, and matching rows from the right table. If no match exists on the right side, NULLs fill those columns."
},
{
"id": 32,
"npc": "Gym Leader Surge",
"text": "What does a RIGHT JOIN return?",
"options": [
"Only matching rows",
"All rows from the LEFT table",
"All rows from the RIGHT table, plus matching left rows (NULLs if no match)",
"Only NULL rows"
],
"answer": 2,
"explanation": "RIGHT JOIN returns ALL rows from the right table, and matching rows from the left table. NULLs appear for unmatched left-side columns. RIGHT JOIN is less common — most prefer LEFT JOIN for readability."
},
{
"id": 33,
"npc": "Gym Leader Surge",
"text": "What does a FULL OUTER JOIN return?",
"options": [
"Only matching rows",
"All rows from the left table only",
"All rows from both tables, with NULLs where there's no match",
"Only non-matching rows"
],
"answer": 2,
"explanation": "FULL OUTER JOIN returns ALL rows from BOTH tables. Where there's no match, NULLs fill the missing side. It combines LEFT and RIGHT JOIN results."
},
{
"id": 34,
"npc": "Erika",
"text": "Grass-type patience is needed here. What is a PRIMARY KEY?",
"options": [
"The first column in a table",
"A column that uniquely identifies each row and cannot be NULL",
"A password for the database",
"The most important column"
],
"answer": 1,
"explanation": "A PRIMARY KEY uniquely identifies each row in a table. It must be unique and cannot be NULL. A table can only have ONE primary key (though it can span multiple columns)."
},
{
"id": 35,
"npc": "Erika",
"text": "What is a FOREIGN KEY?",
"options": [
"A key from another database system",
"A column that links to the PRIMARY KEY of another table",
"A backup primary key",
"An encrypted column"
],
"answer": 1,
"explanation": "A FOREIGN KEY in one table points to the PRIMARY KEY of another table. This creates a relationship between tables. Example: Orders.CustomerID is a FK referencing Customers.CustomerID."
},
{
"id": 36,
"npc": "Koga",
"text": "The art of subtlety... What data type stores whole numbers in T-SQL?",
"options": ["NUMBER", "INT", "WHOLE", "DECIMAL"],
"answer": 1,
"explanation": "INT (integer) stores whole numbers. T-SQL also has TINYINT (0-255), SMALLINT, BIGINT for different ranges. INT is the most commonly used for IDs and counts."
},
{
"id": 37,
"npc": "Koga",
"text": "What T-SQL data type stores text of variable length, commonly used for names and descriptions?",
"options": ["TEXT", "CHAR", "VARCHAR", "STRING"],
"answer": 2,
"explanation": "VARCHAR(n) stores variable-length text up to n characters. Example: VARCHAR(255) stores up to 255 characters but only uses space for actual characters. NVARCHAR supports Unicode."
},
{
"id": 38,
"npc": "Koga",
"text": "What T-SQL data type is best for storing money / currency values?",
"options": ["FLOAT", "CURRENCY", "MONEY", "DECIMAL"],
"answer": 2,
"explanation": "MONEY is a T-SQL-specific type for currency (precise to 4 decimal places). DECIMAL(p,s) is also used. Avoid FLOAT for money — it can introduce rounding errors!"
},
{
"id": 39,
"npc": "Sabrina",
"text": "I can see your future queries! What type stores a date AND time combined in T-SQL?",
"options": ["DATE", "TIME", "DATETIME", "TIMESTAMP"],
"answer": 2,
"explanation": "DATETIME stores both date and time. T-SQL also has DATE (date only), TIME (time only), and DATETIME2 (more precision). GETDATE() returns the current DATETIME."
},
{
"id": 40,
"npc": "Sabrina",
"text": "What T-SQL function returns the current date and time?",
"options": ["NOW()", "CURRENT_DATE()", "GETDATE()", "TODAY()"],
"answer": 2,
"explanation": "GETDATE() returns the current date and time in T-SQL. Example: SELECT GETDATE() returns something like '2024-03-15 14:23:45.000'. This is T-SQL specific — MySQL uses NOW()."
},
{
"id": 41,
"npc": "Blaine",
"text": "Hot like a fire quiz! What SQL statement is used to INSERT new data into a table?",
"options": ["ADD INTO", "INSERT INTO", "PUT INTO", "CREATE ROW"],
"answer": 1,
"explanation": "INSERT INTO adds new rows. Example: INSERT INTO Employees (FirstName, LastName) VALUES ('Ash', 'Ketchum'). You specify columns, then values."
},
{
"id": 42,
"npc": "Blaine",
"text": "What SQL statement MODIFIES existing data in a table?",
"options": ["MODIFY", "CHANGE", "UPDATE", "EDIT"],
"answer": 2,
"explanation": "UPDATE modifies existing rows. Example: UPDATE Employees SET Salary = 50000 WHERE EmployeeID = 1. ALWAYS use WHERE with UPDATE or you'll change EVERY row!"
},
{
"id": 43,
"npc": "Blaine",
"text": "What SQL statement REMOVES rows from a table?",
"options": ["REMOVE", "ERASE", "DROP", "DELETE"],
"answer": 3,
"explanation": "DELETE removes rows. Example: DELETE FROM Employees WHERE EmployeeID = 1. Like UPDATE, ALWAYS use WHERE with DELETE — without it, you'll delete ALL rows in the table!"
},
{
"id": 44,
"npc": "Giovanni",
"text": "You've returned. What's the difference between DELETE and TRUNCATE?",
"options": [
"They are identical",
"DELETE removes specific rows with WHERE; TRUNCATE removes ALL rows and is faster (cannot be rolled back easily)",
"TRUNCATE uses WHERE; DELETE doesn't",
"DELETE is for tables; TRUNCATE is for databases"
],
"answer": 1,
"explanation": "DELETE removes specific rows (can use WHERE) and is logged row-by-row. TRUNCATE removes ALL rows instantly, is faster, and resets identity columns. TRUNCATE cannot be WHERE filtered."
},
{
"id": 45,
"npc": "Lorelei",
"text": "Ice-cold logic! What is a VIEW in SQL?",
"options": [
"A visual chart of the data",
"A saved SELECT query that acts like a virtual table",
"A backup copy of a table",
"A report export"
],
"answer": 1,
"explanation": "A VIEW is a saved SELECT query stored in the database. It acts like a virtual table. Example: CREATE VIEW HighEarners AS SELECT * FROM Employees WHERE Salary > 100000"
},
{
"id": 46,
"npc": "Lorelei",
"text": "What is the benefit of using a VIEW?",
"options": [
"Stores data permanently",
"Simplifies complex queries, improves security by hiding columns, and can be reused",
"Makes queries run faster always",
"Replaces the need for tables"
],
"answer": 1,
"explanation": "VIEWs simplify complex queries (hide joins/logic), improve security (hide sensitive columns like salaries), and can be reused across applications. They don't store data — they run the underlying query each time."
},
{
"id": 47,
"npc": "Bruno",
"text": "Strong queries come from practice! What is a Stored Procedure?",
"options": [
"A saved SELECT query",
"A precompiled set of SQL statements saved in the database that can accept parameters",
"A type of table",
"A database backup process"
],
"answer": 1,
"explanation": "A Stored Procedure (SP) is precompiled SQL code saved in the database. It can accept input/output parameters, contain logic, and be executed with EXEC ProcName. Common in T-SQL!"
},
{
"id": 48,
"npc": "Bruno",
"text": "How do you EXECUTE a stored procedure called 'GetEmployees' in T-SQL?",
"options": ["RUN GetEmployees", "CALL GetEmployees", "EXEC GetEmployees", "START GetEmployees"],
"answer": 2,
"explanation": "EXEC (or EXECUTE) runs a stored procedure. Example: EXEC GetEmployeesByDept @DeptName = 'Sales'. T-SQL uses EXEC; other databases use CALL."
},
{
"id": 49,
"npc": "Agatha",
"text": "Ghosts from the past! What is a TRANSACTION in SQL?",
"options": [
"A financial record in the database",
"A single SQL statement",
"A group of SQL operations treated as one unit — all succeed or all fail",
"A stored procedure"
],
"answer": 2,
"explanation": "A TRANSACTION groups multiple SQL statements so they all succeed or all fail together. This protects data integrity. Example: transferring money requires deducting from one account AND adding to another — both must succeed."
},
{
"id": 50,
"npc": "Agatha",
"text": "What command SAVES a transaction permanently?",
"options": ["SAVE", "APPLY", "COMMIT", "END"],
"answer": 2,
"explanation": "COMMIT saves all changes made in the transaction permanently. Pattern: BEGIN TRANSACTION → (your SQL statements) → COMMIT. If something goes wrong, use ROLLBACK instead."
},
{
"id": 51,
"npc": "Lance",
"text": "Dragon power! What command UNDOES all changes in a transaction?",
"options": ["UNDO", "REVERT", "ROLLBACK", "CANCEL"],
"answer": 2,
"explanation": "ROLLBACK undoes all changes since BEGIN TRANSACTION. This is your emergency undo button. If an error occurs mid-transaction, ROLLBACK returns the database to its previous state."
},
{
"id": 52,
"npc": "Lance",
"text": "What T-SQL keyword is used to declare a variable?",
"options": ["VAR", "SET", "DECLARE", "DIM"],
"answer": 2,
"explanation": "DECLARE creates a variable in T-SQL. Example: DECLARE @EmployeeCount INT. T-SQL variables always start with @. Then SET @EmployeeCount = 100 or SELECT @EmployeeCount = COUNT(*) FROM Employees."
},
{
"id": 53,
"npc": "Lance",
"text": "In T-SQL, what symbol MUST prefix a variable name?",
"options": ["$", "#", "%", "@"],
"answer": 3,
"explanation": "T-SQL variables must start with @. Example: @TotalSales, @EmployeeID, @StartDate. Double @@ means a system variable like @@ROWCOUNT or @@SERVERNAME."
},
{
"id": 54,
"npc": "Professor Oak",
"text": "You've grown so much! What does @@ROWCOUNT return in T-SQL?",
"options": [
"Total rows in the table",
"Number of rows affected by the last SQL statement",
"Number of tables in the database",
"Maximum row count allowed"
],
"answer": 1,
"explanation": "@@ROWCOUNT returns the number of rows affected by the most recent statement. Useful after UPDATE or DELETE to verify how many rows were changed. Example: DELETE ... then IF @@ROWCOUNT = 0 PRINT 'Nothing deleted'"
},
{
"id": 55,
"npc": "Nurse Joy",
"text": "What does ISNULL() do in T-SQL?",
"options": [
"Checks if a value is NULL and returns 1 or 0",
"Replaces NULL with a specified replacement value",
"Deletes NULL rows",
"Converts a column to nullable"
],
"answer": 1,
"explanation": "ISNULL(column, replacement) replaces NULL with the replacement value. Example: SELECT ISNULL(MiddleName, 'N/A') FROM Employees — shows 'N/A' instead of NULL for employees with no middle name."
},
{
"id": 56,
"npc": "Officer Jenny",
"text": "What is the difference between ISNULL() and COALESCE()?",
"options": [
"They are identical",
"ISNULL takes 2 arguments; COALESCE takes multiple and returns the first non-NULL",
"COALESCE is faster",
"ISNULL only works on text"
],
"answer": 1,
"explanation": "ISNULL(a, b) takes exactly 2 args. COALESCE(a, b, c, ...) takes multiple and returns the FIRST non-NULL value. COALESCE is ANSI standard and works across databases. Both are widely used in T-SQL."
},
{
"id": 57,
"npc": "Brock",
"text": "What does the CAST() function do in T-SQL?",
"options": [
"Removes decimal places",
"Converts a value from one data type to another",
"Rounds a number",
"Converts text to uppercase"
],
"answer": 1,
"explanation": "CAST converts data types. Example: CAST('123' AS INT) converts text '123' to the number 123. Or CAST(Salary AS VARCHAR(20)) to display a number as text. CONVERT() is a T-SQL alternative with more formatting options."
},
{
"id": 58,
"npc": "Misty",
"text": "What does LEN() return in T-SQL?",
"options": [
"The lowest value in a column",
"The number of characters in a string",
"The length of a table",
"The line number in a script"
],
"answer": 1,
"explanation": "LEN(string) returns the number of characters. Example: LEN('Hello') returns 5. LEN ignores trailing spaces. Useful for validation — checking if an email address is too long, etc."
},
{
"id": 59,
"npc": "Misty",
"text": "What function converts text to ALL UPPERCASE in T-SQL?",
"options": ["UPPER()", "UPPERCASE()", "CAPS()", "UCASE()"],
"answer": 0,
"explanation": "UPPER(string) converts text to uppercase. LOWER(string) converts to lowercase. Example: WHERE UPPER(LastName) = 'SMITH' — useful for case-insensitive searches (though SQL Server collation also affects this)."
},
{
"id": 60,
"npc": "Gary",
"text": "Still keeping up? What does SUBSTRING() do?",
"options": [
"Removes part of a string",
"Extracts part of a string starting at a position",
"Checks if one string contains another",
"Splits a string into rows"
],
"answer": 1,
"explanation": "SUBSTRING(string, start, length) extracts characters. Example: SUBSTRING('Hello World', 1, 5) returns 'Hello'. Note: T-SQL string positions start at 1, not 0!"
},
{
"id": 61,
"npc": "Scientist Bill",
"text": "What does CONCAT() do in T-SQL?",
"options": [
"Counts the concatenated results",
"Joins two or more strings together",
"Compares two strings",
"Splits a string"
],
"answer": 1,
"explanation": "CONCAT() joins strings together. Example: SELECT CONCAT(FirstName, ' ', LastName) AS FullName FROM Employees. The + operator also concatenates in T-SQL: FirstName + ' ' + LastName."
},
{
"id": 62,
"npc": "Scientist Bill",
"text": "What function extracts the YEAR from a date in T-SQL?",
"options": ["GETYEAR()", "YEAR()", "DATEPART(year,...)", "Both B and C"],
"answer": 3,
"explanation": "Both YEAR(date) and DATEPART(year, date) extract the year. Example: YEAR(HireDate) or DATEPART(year, HireDate). Similarly, MONTH() and DAY() or DATEPART(month/day,...) work the same way."
},
{
"id": 63,
"npc": "Fisherman Ralph",
"text": "What does DATEDIFF() calculate in T-SQL?",
"options": [
"Adds days to a date",
"Formats a date as text",
"The difference between two dates in a specified unit",
"The current date minus a number"
],
"answer": 2,
"explanation": "DATEDIFF(unit, startdate, enddate) calculates the difference between dates. Example: DATEDIFF(year, BirthDate, GETDATE()) gives someone's age in years. Units: year, month, day, hour, minute, second."
},
{
"id": 64,
"npc": "Fisherman Ralph",
"text": "What does DATEADD() do in T-SQL?",
"options": [
"Returns the current date",
"Adds or subtracts a time interval from a date",
"Formats a date",
"Converts text to a date"
],
"answer": 1,
"explanation": "DATEADD(unit, number, date) adds/subtracts time. Example: DATEADD(day, 30, GETDATE()) returns a date 30 days from now. Use negative numbers to go back: DATEADD(month, -6, GETDATE())."
},
{
"id": 65,
"npc": "Hiker Taro",
"text": "What is a subquery?",
"options": [
"A query that runs after the main query",
"A query nested inside another query",
"A secondary database",
"A query with multiple JOINs"
],
"answer": 1,
"explanation": "A subquery is a SELECT statement nested inside another query. Example: SELECT * FROM Employees WHERE Salary > (SELECT AVG(Salary) FROM Employees) — finds employees earning above average."
},
{
"id": 66,
"npc": "Hiker Taro",
"text": "What is a CTE (Common Table Expression)?",
"options": [
"A type of table",
"A temporary named result set defined with WITH that can be referenced in the main query",
"A stored procedure",
"A type of JOIN"
],
"answer": 1,
"explanation": "A CTE uses WITH to create a named temporary result. Example: WITH HighEarners AS (SELECT * FROM Employees WHERE Salary > 100000) SELECT * FROM HighEarners. CTEs improve readability over subqueries."
},
{
"id": 67,
"npc": "Gym Leader Surge",
"text": "What does ROUND() do in T-SQL?",
"options": [
"Removes decimal places entirely",
"Rounds a number to a specified number of decimal places",
"Rounds up always",
"Rounds down always"
],
"answer": 1,
"explanation": "ROUND(number, decimals) rounds to a specified decimal place. Example: ROUND(15.456, 2) returns 15.46. ROUND(15.456, 0) returns 15. Use CEILING() to always round up, FLOOR() to always round down."
},
{
"id": 68,
"npc": "Gym Leader Surge",
"text": "What does CASE WHEN do in T-SQL?",
"options": [
"Handles errors",
"Defines conditional logic — like IF/ELSE inside a SELECT statement",
"Encrypts data",
"Creates a new column permanently"
],
"answer": 1,
"explanation": "CASE WHEN provides conditional logic. Example: SELECT CASE WHEN Salary > 100000 THEN 'High' WHEN Salary > 50000 THEN 'Medium' ELSE 'Low' END AS SalaryBand FROM Employees"
},
{
"id": 69,
"npc": "Erika",
"text": "What is an INDEX in SQL?",
"options": [
"A list of all tables in the database",
"A database object that speeds up data retrieval on a column",
"The first row of a table",
"A numbered list of columns"
],
"answer": 1,
"explanation": "An INDEX speeds up queries by creating a data structure that SQL Server can search quickly — like a book's index. Without indexes, SQL Server scans every row (slow on large tables)."
},
{
"id": 70,
"npc": "Erika",
"text": "What is the difference between a CLUSTERED and NON-CLUSTERED index?",
"options": [
"Clustered physically sorts the table data; non-clustered creates a separate lookup structure",
"Non-clustered is faster always",
"Clustered is for text; non-clustered is for numbers",
"There is no difference"
],
"answer": 0,
"explanation": "A CLUSTERED index physically sorts and stores the table data in order (only one per table — usually the PK). A NON-CLUSTERED index is a separate structure pointing to the data rows. A table can have many non-clustered indexes."
},
{
"id": 71,
"npc": "Koga",
"text": "What does the UNION operator do?",
"options": [
"Joins two tables with a foreign key",
"Combines result sets of two SELECT queries (removing duplicates)",
"Returns only matching rows from two queries",
"Multiplies two result sets"
],
"answer": 1,
"explanation": "UNION combines results from two SELECT statements and removes duplicates. Both queries must have the same number of columns and compatible data types. Use UNION ALL to keep duplicates (faster)."
},
{
"id": 72,
"npc": "Koga",
"text": "What is the difference between UNION and UNION ALL?",
"options": [
"No difference",
"UNION removes duplicates; UNION ALL keeps all rows including duplicates (and is faster)",
"UNION ALL removes duplicates; UNION keeps them",
"UNION ALL adds a total row"
],
"answer": 1,
"explanation": "UNION removes duplicate rows (slower — has to check). UNION ALL keeps ALL rows including duplicates and runs faster. Use UNION ALL when you know there are no duplicates or don't mind them."
},
{
"id": 73,
"npc": "Sabrina",
"text": "What does INTERSECT do?",
"options": [
"Returns all rows from both queries",
"Returns only rows that appear in BOTH query results",
"Returns rows in the first query but not the second",
"Joins two tables"
],
"answer": 1,
"explanation": "INTERSECT returns only rows that exist in BOTH query results. Like a Venn diagram intersection. Less common but useful for finding common records between two datasets."
},
{
"id": 74,
"npc": "Sabrina",
"text": "What does EXCEPT do in T-SQL?",
"options": [
"Returns all rows from both queries",
"Returns rows from the first query that do NOT exist in the second query",
"Excludes a specific column",
"Removes NULL rows"
],
"answer": 1,
"explanation": "EXCEPT returns rows from the FIRST query that don't appear in the SECOND query. Useful for finding records in one dataset that are missing from another. (MySQL uses MINUS instead.)"
},
{
"id": 75,
"npc": "Blaine",
"text": "What is a TRIGGER in SQL?",
"options": [
"A shortcut key in SQL Server Management Studio",
"Automatically executed SQL code when INSERT, UPDATE, or DELETE occurs on a table",
"A type of stored procedure that returns a value",
"A way to schedule queries"
],
"answer": 1,
"explanation": "A TRIGGER automatically fires when a specified event (INSERT, UPDATE, DELETE) happens on a table. Used for auditing, enforcing business rules, or cascading changes. Use carefully — they can slow performance."
},
{
"id": 76,
"npc": "Lorelei",
"text": "What is a SCHEMA in SQL Server?",
"options": [
"The visual diagram of a database",
"A container/namespace that groups related database objects together",
"A type of backup",
"The database itself"
],
"answer": 1,
"explanation": "A schema is a namespace that organizes database objects. Example: dbo.Employees (schema 'dbo', table 'Employees'). Common schemas: dbo (default), HR, Finance, Sales. Like folders for database objects."
},
{
"id": 77,
"npc": "Lorelei",
"text": "In T-SQL, what does SELECT TOP 1 ... ORDER BY Date DESC return?",
"options": [
"The oldest record",
"All records sorted by date",
"The most recent (latest) single record",
"A random record"
],
"answer": 2,
"explanation": "TOP 1 limits to 1 row. ORDER BY Date DESC sorts newest first. Combined, this returns the SINGLE most recent record. This pattern is very common in real-world T-SQL queries!"
},
{
"id": 78,
"npc": "Bruno",
"text": "What does SELECT INTO do in T-SQL?",
"options": [
"Moves data from one table to another permanently",
"Creates a NEW table and inserts the query results into it",
"Inserts data into an existing table",
"Creates a view"
],
"answer": 1,
"explanation": "SELECT ... INTO NewTable FROM ... creates a NEW table and inserts query results. Example: SELECT * INTO Employees_Backup FROM Employees. The new table structure matches the query result."
},
{
"id": 79,
"npc": "Bruno",
"text": "What is INSERT INTO ... SELECT used for?",
"options": [
"Creates a new table",
"Copies data from one query result into an EXISTING table",
"Updates existing rows",
"Creates a view from a table"
],
"answer": 1,
"explanation": "INSERT INTO ExistingTable SELECT ... FROM ... copies data INTO an EXISTING table. Different from SELECT INTO (which CREATES a new table). The target table must already exist and match the column structure."
},
{
"id": 80,
"npc": "Agatha",
"text": "From the shadows... What is a TEMP TABLE in T-SQL?",
"options": [
"A table that deletes itself after 1 hour",
"A temporary table stored in tempdb that exists only for the current session",
"A view that looks like a table",
"A table with no indexes"
],
"answer": 1,
"explanation": "Temp tables (#TableName) are stored in tempdb and exist only for your session (or procedure). They're great for storing intermediate results. ## prefix makes it a global temp table visible to all sessions."
},
{
"id": 81,
"npc": "Agatha",
"text": "What is a TABLE VARIABLE in T-SQL and how does it differ from a temp table?",
"options": [
"They are identical",
"A table variable (@TableName) exists only within a batch/procedure and is stored in memory (usually)",
"Table variables are permanent",
"Table variables use disk; temp tables use memory"
],
"answer": 1,
"explanation": "A table variable (DECLARE @MyTable TABLE(...)) is scoped to the current batch/procedure. They often live in memory (small data), are faster for small datasets, but can't have indexes easily. Temp tables are better for large datasets."
},
{
"id": 82,
"npc": "Lance",
"text": "What does TRY...CATCH do in T-SQL?",
"options": [
"Tests query performance",
"Handles errors gracefully — runs TRY block, and if error occurs, executes CATCH block",
"Validates data before insert",
"Encrypts sensitive data"
],
"answer": 1,
"explanation": "TRY...CATCH is T-SQL error handling. Code in TRY block runs normally. If an error occurs, execution jumps to CATCH where you can log the error, ROLLBACK a transaction, or return a friendly message."
},
{
"id": 83,
"npc": "Lance",
"text": "What does @@ERROR return in T-SQL?",
"options": [
"The error message text",
"The error number of the last statement (0 if no error)",
"The line number of the error",
"A list of all recent errors"
],
"answer": 1,
"explanation": "@@ERROR returns the error number from the last T-SQL statement. 0 means success. Older code uses @@ERROR; modern T-SQL prefers TRY...CATCH with ERROR_NUMBER(), ERROR_MESSAGE(), ERROR_LINE() functions."
},
{
"id": 84,
"npc": "Rival Gary",
"text": "OK you're actually pretty good. What is SQL Server Management Studio (SSMS)?",
"options": [
"A type of SQL Server database",
"Microsoft's free GUI tool for connecting to, managing, and querying SQL Server databases",
"A stored procedure for managing users",
"A cloud version of SQL Server"
],
"answer": 1,
"explanation": "SSMS is Microsoft's free IDE for SQL Server. You use it to write and run T-SQL queries, manage databases, create tables/views/procedures, check performance, and administer SQL Server. Every DBA uses it daily!"
},
{
"id": 85,
"npc": "Nurse Joy",
"text": "What does a query execution plan show you in SQL Server?",
"options": [
"The query results in a graphical format",
"How SQL Server plans to physically execute your query — showing operations, costs, and bottlenecks",
"A list of scheduled queries",
"The query history"
],
"answer": 1,
"explanation": "An Execution Plan (view with Ctrl+M in SSMS) shows HOW SQL Server will execute your query — table scans, index seeks, joins, sorts, and their relative cost %. Essential for query performance tuning!"
},
{
"id": 86,
"npc": "Officer Jenny",
"text": "What does the NOLOCK hint do in a SELECT query?",
"options": [
"Prevents other users from reading the table",
"Allows reading data without taking a lock — faster but may read uncommitted/dirty data",
"Encrypts the query results",
"Prevents the query from timing out"
],
"answer": 1,
"explanation": "WITH (NOLOCK) hint allows dirty reads — reading data even if another transaction hasn't committed yet. Makes reads faster and reduces blocking, but risks reading data that gets rolled back. Common in reporting queries."
},
{
"id": 87,
"npc": "Professor Oak",
"text": "What is a DEADLOCK in SQL Server?",
"options": [
"When a query takes too long",
"When two processes each wait for the other to release a lock, causing an infinite wait",
"When the database runs out of storage",
"When an index is corrupt"
],
"answer": 1,
"explanation": "A deadlock occurs when Process A holds a lock that Process B wants, and Process B holds a lock that Process A wants — neither can proceed. SQL Server detects this and kills one process (the 'deadlock victim')."
},
{
"id": 88,
"npc": "Scientist Bill",
"text": "What does ROW_NUMBER() do in T-SQL?",
"options": [
"Counts the total rows in a table",
"Assigns a sequential number to each row within a result set partition",
"Returns the row's physical position in the table",
"Adds an ID column permanently"
],
"answer": 1,
"explanation": "ROW_NUMBER() is a window function that numbers rows. Example: SELECT ROW_NUMBER() OVER (ORDER BY Salary DESC) AS Rank, * FROM Employees. Used for ranking, pagination, and removing duplicates."
},
{
"id": 89,
"npc": "Scientist Bill",
"text": "What is the difference between ROW_NUMBER(), RANK(), and DENSE_RANK()?",
"options": [
"They are identical",
"ROW_NUMBER gives unique sequential numbers; RANK skips numbers on ties; DENSE_RANK does not skip on ties",
"RANK is the fastest; others are aliases",
"ROW_NUMBER requires a PARTITION BY"
],
"answer": 1,
"explanation": "For tied values: ROW_NUMBER gives 1,2,3 (always unique). RANK gives 1,1,3 (skips 2 after tie). DENSE_RANK gives 1,1,2 (no skipping). All are window functions used with OVER(ORDER BY ...)."
},
{
"id": 90,
"npc": "Erika",
"text": "What does PARTITION BY do inside a window function?",
"options": [
"Splits the database into sections",
"Resets the window function calculation for each group defined by the partition column(s)",
"Creates a backup partition",
"Divides a number evenly"
],
"answer": 1,
"explanation": "PARTITION BY divides rows into groups for window functions. Example: ROW_NUMBER() OVER (PARTITION BY Department ORDER BY Salary DESC) numbers employees 1,2,3... within EACH department separately."
},
{
"id": 91,
"npc": "Koga",
"text": "What does the PIVOT operation do in T-SQL?",
"options": [
"Rotates rows into columns — converts unique values from one column into multiple columns",
"Sorts data clockwise",
"Transposes the entire table",
"Converts columns to rows"
],
"answer": 0,
"explanation": "PIVOT rotates rows into columns. Example: turning a Sales table with rows for each month into a summary with columns Jan, Feb, Mar... Very useful for reporting and creating crosstab summaries."
},
{
"id": 92,
"npc": "Blaine",
"text": "Scorching hot question! What is the IDENTITY property in T-SQL?",
"options": [
"Stores the user's login name",
"An auto-incrementing number column — SQL Server automatically generates a unique value for each new row",
"A unique constraint on a column",
"The database's license ID"
],
"answer": 1,
"explanation": "IDENTITY(seed, increment) auto-generates values. Example: EmployeeID INT IDENTITY(1,1) starts at 1 and increments by 1 for each new row. Common for primary keys. Use @@IDENTITY or SCOPE_IDENTITY() to get the last generated value."
},
{
"id": 93,
"npc": "Lorelei",
"text": "What is the difference between CHAR and VARCHAR data types?",
"options": [
"No difference",
"CHAR is fixed-length (always uses full allocated space); VARCHAR is variable-length (uses only space needed)",
"VARCHAR is faster for all use cases",
"CHAR is for numbers; VARCHAR is for text"
],
"answer": 1,
"explanation": "CHAR(10) always uses 10 characters of storage (pads with spaces). VARCHAR(10) uses only the space the actual value needs. CHAR is efficient for fixed-length data (like state codes 'CA', 'NY'). VARCHAR is better for variable-length text."
},
{
"id": 94,
"npc": "Bruno",
"text": "What is the NVARCHAR data type used for?",
"options": [
"Negative numbers stored as text",
"Unicode text — supports international characters like Chinese, Arabic, emoji",
"Numbers with variable decimal places",
"Very long text over 8000 characters"
],
"answer": 1,
"explanation": "NVARCHAR stores Unicode text (N stands for National). It uses 2 bytes per character, supporting any language's characters. Use NVARCHAR when your data may contain non-English characters. Prefix Unicode strings with N: N'Héllo'."
},
{
"id": 95,
"npc": "Agatha",
"text": "What does a CHECK constraint do?",
"options": [
"Checks if the table has data",
"Enforces that column values meet a specified condition before INSERT/UPDATE",
"Verifies the database connection",
"Checks for duplicate rows"
],
"answer": 1,
"explanation": "CHECK constraints enforce data rules. Example: CHECK (Age >= 18) prevents inserting anyone younger than 18. CHECK (Salary > 0) ensures salary is positive. They protect data integrity at the database level."
},
{
"id": 96,
"npc": "Lance",
"text": "What is database NORMALIZATION?",
"options": [
"Converting all text to lowercase",
"The process of organizing tables to reduce data redundancy and improve integrity",
"Sorting all tables alphabetically",
"Defragmenting the database"
],
"answer": 1,
"explanation": "Normalization organizes data to minimize redundancy. 1NF: eliminate repeating groups. 2NF: remove partial dependencies. 3NF: remove transitive dependencies. Well-normalized databases are easier to maintain and have fewer update anomalies."
},
{
"id": 97,
"npc": "Rival Gary",
"text": "What is the purpose of the sp_help stored procedure in SQL Server?",
"options": [
"Returns help documentation in a browser",
"Returns information about a database object — its columns, types, constraints, and indexes",
"Lists all stored procedures",
"Shows the SQL Server error log"
],
"answer": 1,
"explanation": "EXEC sp_help 'TableName' returns detailed info about a table: columns, data types, nullability, constraints, indexes. Great for quickly understanding an unfamiliar table's structure without opening Object Explorer."
},
{
"id": 98,
"npc": "Professor Oak",
"text": "Nearly there, trainer! What does sp_who2 return in SQL Server?",
"options": [
"A list of all stored procedures",
"Information about current user sessions and processes — who is connected and what they're running",
"The database owner information",
"All SQL Server logins"
],
"answer": 1,
"explanation": "EXEC sp_who2 shows active connections: login names, status, blocking info, CPU, disk usage, and current command. DBAs use it to find blocking queries, idle connections, or who is running slow queries."
},
{
"id": 99,
"npc": "Champion",
"text": "One question from glory! What is the difference between a clustered index SEEK and a TABLE SCAN in execution plans?",
"options": [
"No difference in performance",
"Index Seek directly finds matching rows (fast); Table Scan reads every row in the table (slow on large tables)",
"Table Scan uses indexes; Index Seek does not",
"Index Seek is only for text columns"
],
"answer": 1,
"explanation": "Index SEEK is like using a book index — goes directly to the data. Table SCAN reads every single row. Seeks are almost always faster on large tables. Seeing Table Scans in execution plans often signals a missing index."
},
{
"id": 100,
"npc": "Champion",
"text": "FINAL QUESTION! You are writing a query for management to show total sales by region, only for regions with over $1,000,000 in sales, sorted highest first. Which query structure is correct?",
"options": [
"SELECT Region, SUM(Amount) AS TotalSales FROM Sales WHERE SUM(Amount) > 1000000 GROUP BY Region ORDER BY TotalSales DESC",
"SELECT Region, SUM(Amount) AS TotalSales FROM Sales GROUP BY Region HAVING SUM(Amount) > 1000000 ORDER BY TotalSales DESC",
"SELECT Region, SUM(Amount) AS TotalSales FROM Sales GROUP BY Region WHERE TotalSales > 1000000 ORDER BY TotalSales DESC",
"SELECT Region, SUM(Amount) AS TotalSales FROM Sales HAVING SUM(Amount) > 1000000 GROUP BY Region ORDER BY TotalSales DESC"
],
"answer": 1,
"explanation": "Correct! GROUP BY Region groups the data, HAVING filters the groups (you can't use WHERE with aggregate functions), and ORDER BY TotalSales DESC sorts highest first. This is a real-world query pattern used every day by analysts and DBAs!"
}
]
}
]
}
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