摘要：
1.inner join ,left join 与 right join (from 百度知道)例表aaid adate1 a12 a23 a3表bbid bdate1 b12 b24 b4(1)两个表a,b相连接,要取出id相同的字段select * from a inner join b on a.aid = b.bid此时的取出的是:1 a1 b12 a2 b2(2)left join 指:select * from a left join b on a.aid = b.bid首先取出a表中所有数据,然后再加上与a,b匹配的的数据此时的取出的是:1 a1 b12 a2 b23 a3 空字 阅读全文
