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Questions and Answers
What does the SQL condition 'WHERE column BETWEEN ... AND ...' achieve?
What does the SQL condition 'WHERE column BETWEEN ... AND ...' achieve?
In SQL, how does the 'LIKE' operator operate?
In SQL, how does the 'LIKE' operator operate?
Which of the following SQL queries correctly uses the 'IN' clause?
Which of the following SQL queries correctly uses the 'IN' clause?
What does the SQL clause 'WHERE column IS NULL' determine?
What does the SQL clause 'WHERE column IS NULL' determine?
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If you want to combine multiple conditions in a SQL query, which operator can be used?
If you want to combine multiple conditions in a SQL query, which operator can be used?
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In the statement 'SELECT * FROM EMPLOYEES WHERE SALARY > 300 AND STORE_ID = 2', what is required?
In the statement 'SELECT * FROM EMPLOYEES WHERE SALARY > 300 AND STORE_ID = 2', what is required?
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What does the percentage symbol '%' represent in SQL 'LIKE' conditions?
What does the percentage symbol '%' represent in SQL 'LIKE' conditions?
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How is 'NOT' used in SQL conditions?
How is 'NOT' used in SQL conditions?
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Study Notes
SQL WHERE Clause
- The WHERE clause filters records in a table
- It uses comparison operators like =, >, <, >=, <=, <> (not equal to)
- Example:
SELECT * FROM EMPLOYEES WHERE SALARY > 600
SQL WHERE BETWEEN ... AND
- The BETWEEN operator selects values within a range
- Includes the start and end values
- Example:
SELECT * FROM PRODUCTS WHERE PRICE BETWEEN 10 AND 20
SQL WHERE IN
- The IN operator selects rows where a column's value matches one of a list of values.
- Example:
SELECT * FROM CUSTOMERS WHERE CITY IN ('London', 'Paris', 'New York')
SQL WHERE LIKE
- The LIKE operator filters for values matching a pattern
- Uses wildcards:
%(matches any sequence of characters),_(matches any single character) - Example:
SELECT * FROM USERS WHERE NAME LIKE 'J%'(finds names starting with 'J')
SQL WHERE NULL
- NULL represents missing or unknown values
- The IS NULL operator tests for NULL values
- Example:
SELECT * FROM ORDERS WHERE DELIVERY_DATE IS NULL
SQL WHERE (NOT, AND, OR)
- Combining multiple conditions with AND, OR, NOT
- AND requires all conditions to be true
- OR requires at least one condition to be true
- NOT reverses a condition
- Example:
SELECT * FROM ORDERS WHERE STATUS = 'Shipped' AND CUSTOMER_ID = 101
SQL WHERE (ORDER BY)
- Sorts query results
- Ascending order (by default):
- Example: SELECT * FROM PRODUCTS ORDER BY PRICE
- Descending order use DESC
- Example: SELECT * FROM PRODUCTS ORDER BY PRICE DESC
SQL (DISTINCT)
-
Selects only unique values for a column.
-
Example:
SELECT DISTINCT CITY FROM CUSTOMERS
SQL (LOWER/UPPER)
- LOWER transforms text to lowercase.
- UPPER transforms text to uppercase.
SQL (CONCAT)
- Joins strings together into a new string
- Example:
SELECT CONCAT(FirstName,' ',LastName) AS FullName
SQL (Aggregate Functions)
- Used with
GROUP BYclause to perform calculations on values within that group - Examples:
- AVG(): Calculates the average
- COUNT(): Counts rows
- MAX(): Finds the maximum value
- MIN(): Finds the minimum value
- SUM(): Calculates the sum
SQL (HAVING)
- Filters groups after a
GROUP BYoperation. - Example: selects customers who have placed more than two orders
-
SELECT COUNT(*), CustomerID FROM Orders GROUP BY CustomerID HAVING COUNT(*) > 2
General SQL Syntax and Structure
-
SELECTclause specifies which columns to retrieve -
FROMclause specifies which table to retrieve data from -
WHEREclause filters the data based on conditions -
GROUP BYclause groups rows with the same values in specified columns -
HAVINGclause filters groups based on conditions -
ORDER BYclause sorts results
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Description
Test your knowledge of SQL's WHERE clause concepts! This quiz covers various aspects of filtering records, including the use of comparison operators, the BETWEEN operator, IN operator, LIKE operator, and handling NULL values. Sharpen your SQL skills with these practical examples and explanations.
