ALTER和UPDATE的区别

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UPDATE用来更新表的数据

ALTER用来更新表的结构

 

打个比方一个表有多字段，字段里面有数据

比作一个楼里有很多房间，房间里面有家具

alter是改房间，update是改家具

 

用法，表名是"你家"

在你家加个字段"厕所"就是

ALTER TABLE 你家 ADD 厕所 VARCHAR( 8 )

VARCHAR( 8 )表示8平米

把你家厨房改厕所就是

ALTER TABLE 你家 CHANGE 厨房 厕所 VARCHA(8)

 

在厕所改马桶就是（你家以前是蹲式马桶）

update 你家 set 厕所=坐式马桶