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2025-01-16 Update From: SLTechnology News&Howtos shulou NAV: SLTechnology News&Howtos > Database >
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What is the difference between DELETE and DROP in SQL? This article uses the example code to show, the code is very detailed, which can be used for reference by interested friends. I hope it will be helpful to you.
A brief introduction to the DELETE command
DELETE is a data manipulation language (DDL) command that can be used to delete some or all records from a table using the DELETE command. Can be used with the WHERE clause to delete some records that meet the added condition; if no WHERE condition is specified, all records will be deleted. [recommended for related video tutorials: MySQL tutorial]
Note: you cannot delete an entire table or field or constraint using the DELETE command.
The syntax of the DELETE command is:
DELETE FROM relation_name where condition
If you use a foreign key to link two tables and delete tuples from the referenced table, the data in the referenced table is also automatically deleted to maintain referential integrity.
A brief introduction to the DROP command
DROP is a data definition language (DDL) command that deletes one or more tables from a database. It deletes all related data, indexes, triggers, constraints, and permission specifications for the table.
The syntax of the DROP command is:
DROP SCHEMA schema_name RESTRICT;DROP Table table_name CASCADE
The DROP command has two behavior options named CASCADE and RESTRICT. When CASCADE is used in DROP schemas, it deletes all relevant elements, such as schemas, fields, and all tables in constraints.
When we use CASCADE to delete a table from a schema, it deletes all constraints, views, and elements that reference the relationship being deleted.
Note: tables referenced by any foreign key constraints cannot be deleted.
Main differences between DELETE and DROP
1. DELETE is a data manipulation language command, while DROP is a data definition language command.
2. The DELETE command is used to delete some or all tuples from the table. On the other hand, the DROP command is used to delete one or more tables from the database, and all related data, indexes, triggers, constraints, and permission specifications for the table can be deleted.
3. DELETE can be used with the WHERE clause, but DROP cannot be used with any command.
4. You can use the DELETE command to perform a rollback operation because it uses buffers; however, you cannot operate a rollback with the DROP command because it processes the actual data directly.
5. Since the DELETE command does not delete the table, no space is freed, while the drop command deletes the entire table, freeing up memory space.
These are the details of DELETE and DROP in SQL. Have you learned anything after reading them? If you want to know more about it, you are welcome to follow the industry information!
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