DELETE Statement in SQL

DELETE Statement in SQL

Introduction The DELETE statement in SQL is used to delete one or more rows from a table in a database. It allows you to remove specific records that match a certain condition or delete all records from a table. The DELETE statement is part of the Data Manipulation Language (DML) and is commonly used in combination with the SELECT statement to filter the data that needs to be deleted.

Syntax The basic syntax of the DELETE statement is as follows:

sql
DELETE FROM table_name
WHERE condition;

• DELETE FROM: Specifies the table from which you want to delete data.
• table_name: Specifies the name of the table.
• WHERE: Optional clause that allows you to specify a condition for deleting the rows. If omitted, all rows from the table will be deleted.
• condition: Specifies the condition that determines which rows will be deleted.

Example 1: Deleting All Rows from a Table

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DELETE FROM employees;

In this example, the DELETE statement deletes all rows from the "employees" table. It doesn't include a WHERE clause, so all records are removed.

Example 2: Deleting Rows Based on a Condition

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DELETE FROM customers
WHERE city = 'London';

In this example, the DELETE statement deletes rows from the "customers" table where the city is 'London'. Only the rows that match the specified condition will be deleted.

Example 3: Deleting Multiple Rows

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DELETE FROM orders
WHERE order_date < '2023-01-01';

In this example, the DELETE statement deletes rows from the "orders" table where the order_date is before '2023-01-01'. All rows that satisfy the condition will be deleted.

Important Points to Note

• The DELETE statement permanently removes data from a table. Make sure to use it with caution and double-check the condition before executing.
• If you omit the WHERE clause in a DELETE statement, it will delete all rows from the specified table.
• The DELETE statement can be used in conjunction with other clauses like JOIN to delete rows from multiple tables based on a condition.

Conclusion The DELETE statement in SQL is a powerful tool for removing data from a table. It allows you to delete specific rows or all rows from a table based on specified conditions. Understanding how to use the DELETE statement effectively is crucial for managing and maintaining data integrity in a database.