SQL DELETE Statement and Syntax

Which clause is used in SQL to specify the condition for deleting rows from a table?

What will be the result of the following SQL statement? DELETE FROM Users WHERE Age > 30;

Which of the following SQL statements will delete all rows from the Employees table where the FirstName column value is 'John'?

Suppose you have a table named Orders with columns OrderID, CustomerName, and OrderDate. Which SQL statement will delete all orders placed before January 1, 2022?

Which of the following SQL statements will delete all rows from the Products table where the ProductName is NULL?

What is the purpose of the DELETE statement in SQL?

SQL Delete Syntax

The DELETE statement is a powerful feature in SQL databases that allows you to remove specific information from your tables. However, it is crucial to exercise caution when using DELETE, as once executed, the data cannot be recovered unless you restore the database from a backup.

Basic Syntax

The simplest form of a DELETE query consists of the DELETE keyword followed by the table name. For instance, DELETE FROM MyTable; would delete all rows within MyTable.

DELETE FROM MyTable;

Conditional Deletion

To delete specific information based on a condition, you can utilize the DELETE statement along with the WHERE clause. The WHERE clause is used to specify which rows should be removed from the table by referencing a condition. For example, if you want to delete all employees who are older than 30 years, you can use the following query:

DELETE FROM Employees WHERE Age > 30;

This query will remove all records where the Age column value exceeds 30.

Examples

Example 1

Let's consider a simple user list in a database. We have a table named "Users" with UserID, FirstName, LastName, Age columns. To remove users based on age:

DELETE FROM Users WHERE Age > 30;

Example 2

Assuming we had not already deleted William Garcia in the previous example, he would be removed based on our condition:

DELETE FROM Users WHERE Name = 'William';

Remember that these examples are just for illustration purposes. Always verify the need for such operations and consider data backups before running any DELETE queries.

Learn about the DELETE statement in SQL, its basic syntax for deleting all rows or specific information based on conditions using the WHERE clause. Exercise caution as deleted data cannot be recovered without a database backup. Includes examples for practical understanding.