What is the mysql statement to delete data?
The mysql statement to delete data is "DELETE", which can delete one or more rows of data in the data table. The syntax format is "DELETE FROM
[WHERE clause] [ORDER BY clause] [LIMIT clause]".
The operating environment of this tutorial: windows7 system, mysql8 version, Dell G3 computer.
In MySQL, you can use the DELETE statement to delete one or more rows of data in a table.
DELETE statement can delete data from a single table. The syntax format is:
DELETE FROM <表名> [WHERE 子句] [ORDER BY 子句] [LIMIT 子句]Copy after loginThe syntax description is as follows:
- ##
: Specify the table name from which data is to be deleted.
- ORDER BY clause: Optional. Indicates that when deleting, rows in the table will be deleted in the order specified in the clause.
- WHERE clause: Optional. Indicates that the deletion conditions are limited for the deletion operation. If this clause is omitted, it means that all rows in the table are deleted.
- LIMIT clause: Optional. Used to tell the server the maximum number of rows to be deleted before the control command is returned to the client.
Note: When the WHERE condition is not used, all data will be deleted.Usage example of DELETE statement
Delete all data in the table
[Example 1] Delete all data in the tb_courses_new tablemysql> DELETE FROM tb_courses_new; Query OK, 3 rows affected (0.12 sec) mysql> SELECT * FROM tb_courses_new; Empty set (0.00 sec)Copy after loginDelete data in the table based on conditions
[Example 2] In the tb_courses_new table, delete the course_id as 4 The recordIt can be seen from the running results that the record with course_id 4 has been deleted. [Related recommendations:mysql> DELETE FROM tb_courses -> WHERE course_id=4; Query OK, 1 row affected (0.00 sec) mysql> SELECT * FROM tb_courses; +-----------+-------------+--------------+------------------+ | course_id | course_name | course_grade | course_info | +-----------+-------------+--------------+------------------+ | 1 | Network | 3 | Computer Network | | 2 | Database | 3 | MySQL | | 3 | Java | 4 | Java EE | +-----------+-------------+--------------+------------------+ 3 rows in set (0.00 sec)Copy after loginmysql video tutorial]
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See all articlesMySQL is an open source relational database management system. 1) Create database and tables: Use the CREATEDATABASE and CREATETABLE commands. 2) Basic operations: INSERT, UPDATE, DELETE and SELECT. 3) Advanced operations: JOIN, subquery and transaction processing. 4) Debugging skills: Check syntax, data type and permissions. 5) Optimization suggestions: Use indexes, avoid SELECT* and use transactions.
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Recovering deleted rows directly from the database is usually impossible unless there is a backup or transaction rollback mechanism. Key point: Transaction rollback: Execute ROLLBACK before the transaction is committed to recover data. Backup: Regular backup of the database can be used to quickly restore data. Database snapshot: You can create a read-only copy of the database and restore the data after the data is deleted accidentally. Use DELETE statement with caution: Check the conditions carefully to avoid accidentally deleting data. Use the WHERE clause: explicitly specify the data to be deleted. Use the test environment: Test before performing a DELETE operation.
