mysql多表添加查询

给你几个情况

1.如果是累加name是这样的

update

b

set

name=name+a.name

from

a

where

a.url=b.http

2.直接插入

insert

b(name)

select

name

from

a

join

b

on

a.url=b.http

3.替换原来的name

update

b

set

name=a.name

from

a

where

a.url=b.http

通过AUTO_INCREMENT设置SQLINSERT语句的时候，要避免指定那个自增的字段.否则会发生主键的冲突。通过ALTERTABLE语句可以修改自增的数值，但是只能增加，不能减少。TRUNCATETABLE语句，会将自增ID重置为零。mysqlCREATETABLEtest_create_tab2(-idINTAUTO_INCREMENT,-valVARCHAR(10),-PRIMARYKEY(id)-)QueryOK,0rowsaffected(0.09sec)mysqlINSERTINTOtest_create_tab2(val)VALUES('NOid')QueryOK,1rowaffected(0.03sec)mysqlselectlast_insert_id()asid+----+|id|+----+|1|+----+1rowinset(0.00sec)mysqlINSERTINTOtest_create_tab2(val)VALUES('NOid2')QueryOK,1rowaffected(0.03sec)mysqlselectlast_insert_id()asid+----+|id|+----+|2|+----+1rowinset(0.00sec)mysqlselect*fromtest_create_tab2+----+---------+|id|val|+----+---------+|1|NOid||2|NOid2|+----+---------+2rowsinset(0.00sec)

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