DML数据操纵语言(UPDATE)

UPDATE

语法:

UPDATE 表名  SET 字段名='要修改的数据' [where 条件判断1 and 条件判断2]
例:
/*以下数据表为例*/
+-----+------+---------+-------+-------+
| id  | name | address | grade | level |
+-----+------+---------+-------+-------+
| 100 | CYJ  | bj      |  80.0 | good  |
| 101 | PJF  | tj      |  95.0 | best  |
+-----+------+---------+-------+-------+

mysql> UPDATE test1 SET name='test';/*不加where条件判断修改整个表的字段数据更新*/
/*整个表的name字段都改为test*/
+-----+------+---------+-------+-------+
| id  | name | address | grade | level |
+-----+------+---------+-------+-------+
| 100 | test | bj      |  80.0 | good  |
| 101 | test | tj      |  95.0 | best  |
+-----+------+---------+-------+-------+

mysql> UPDATE test1 SET name='test10' WHERE id=100;/*只修改单条数据的指定字段*/
/*只有id为100的数据记录中的name有修改*/
+-----+--------+---------+-------+-------+
| id  | name   | address | grade | level |
+-----+--------+---------+-------+-------+
| 100 | test10 | bj      |  80.0 | good  |
| 101 | test   | tj      |  95.0 | best  |
+-----+--------+---------+-------+-------+

​ 如果UPDATE需要修改若干数据中的一条,需要保证该数据的筛选条件可以在表中筛选出唯一值进行修改,否则会造成多条数据被修改的情况

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