MYSQL-删改

Posted 2021-11-27

删除

delete：
DELETE [LOW_PRIORITY] [QUICK] [IGNORE] FROM tbl_name
[WHERE where_condition]
[ORDER BY ...]
[LIMIT row_count]

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注意：
需要的注意的是，一定要有限制条件，否则清空所有表数据
限制条件：
where
limit
删除前请三思，确认表中数据无用，再ENTER

示例

删除db1所有数据，相当于清空点db1表

delete from db1;

给定条件删除数据，

delete from copy where age=100；

还可以先进行条件过滤，然后删除指定的字段

delete from copy where age > 50 order by age desc limit 1;

修改

UPDATE [LOW_PRIORITY] [IGNORE] table_reference
SET col_name1={expr1|DEFAULT} [, col_name2={expr2|DEFAULT}] ...
[WHERE where_condition]
[ORDER BY ...]
[LIMIT row_count]

示例：

修改copy表中age 字段的值为22,

update copy set age=22;

修改指定id号的name字段

update copy set name=‘hyt‘ where id=24;

修改指定id号的多个字段

updata copy set name=‘hyt‘,age=‘22‘ where id=13;

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请各位大佬多多指教