Delete data from SQL tables

What is the meaning of Deleting Data in SQL?

Before dive into the technicalities, let's clarify what is the meaning of Deleting Data in SQL. In SQL, deleting data refers to the process of removing specific records or all records from a table, depending on your requirements. This action is irreversible, and once data is deleted, it cannot be recovered unless you have a backup in place.

Understanding the Basics

The DELETE statement is used to remove data from a SQL table. The way that this statement works is as follows:

DELETE FROM table_name WHERE condition;

• DELETE FROM signals the beginning of the deletion process.
• table_name specifies the name of the table from which you want to delete data.
• WHERE condition (optional) allows you to define specific criteria that must be met for a row to be deleted.

Deleting All Rows

If you omit the WHERE clause, SQL will interpret your command as a request to delete all rows in the table. It's a powerful and potentially dangerous action, so use it with caution:

DELETE FROM table_name;

Differentiating DELETE and TRUNCATE

It's common for beginners to confuse the DELETE statement with another SQL command, TRUNCATE. Let's clarify the distinctions:

DELETE Statement

• Deletes rows based on specified conditions.
• Can delete specific rows or all rows.
• Does not release space occupied by the table.
• Ideal for precise data removal.

TRUNCATE Statement

• Deletes all rows from a table.
• Frees up the space occupied by the table.
• Does not require a WHERE clause.
• Faster for removing all data but lacks condition-based precision.

DROP vs. DELETE: Know the Difference

When it comes to table management in SQL, it's essential to understand the difference between DROP and DELETE:

DROP Statement Deletes the entire table, including its structure. Invalidates all relationships with other tables. Erases integrity constraints. Removes access privileges. Use with extreme caution, as it's irreversible.

DELETE Statement Deletes data rows, preserving the table structure. Maintains table relationships. Retains integrity constraints. Preserves access privileges. Provides more granular control over data removal.