select a.id,a.a1,a.a2,a.a3, b.b1,b.b2,b.b3, c.c1,c.c2,c.c3 from a,b,c where a.id*=b.id and a.id*=c.id
select a.id,a.a1,a.a2,a.a3, b.b1,b.b2,b.b3, c.c1,c.c2,c.c3 from a join b on a.id=b.id join c on c.id=a.id
晕 连接啊 用内连接 inner join 或者sql-92标准连接方法 --用inner join select id,a1,a2,a3,b1,b2,b3,c1,c2,c3 from a,b,c where a.id = b.id and a.id = c.id--SQL92标准 select id,a1,a2,a3,b1,b2,b3,c1,c2,c3 from a inner join b on a.id = b.id inner join c on c.id = a.id
这样做那不是不能把a,b,c3个表的id不同的查出来吗?
select a.id,a.a1,a.a2,a.a3, b.b1,b.b2,b.b3, c.c1,c.c2,c.c3 from a,b,c where a.id=b.id and a.id=c.id这样是不行的,这样只会把ID相同的记录查出来,但是我的不同的呢?
select x.id,a.a1,a.a2,a.a3, b.b1,b.b2,b.b3, c.c1,c.c2,c.c3 from (select id from a1 union select id from a2 union select id from a3) x, a,b,c where x.id=a.id and x.id=b.id and x.id=c.id
a.id,a.a1,a.a2,a.a3,
b.b1,b.b2,b.b3,
c.c1,c.c2,c.c3
from
a,b,c
where
a.id*=b.id and a.id*=c.id
b.b1,b.b2,b.b3,
c.c1,c.c2,c.c3
from a
join b
on a.id=b.id
join c
on c.id=a.id
--用inner join
select id,a1,a2,a3,b1,b2,b3,c1,c2,c3 from a,b,c
where a.id = b.id and a.id = c.id--SQL92标准
select id,a1,a2,a3,b1,b2,b3,c1,c2,c3 from a
inner join b
on a.id = b.id
inner join c
on c.id = a.id
a.id,a.a1,a.a2,a.a3,
b.b1,b.b2,b.b3,
c.c1,c.c2,c.c3
from
a,b,c
where
a.id=b.id and a.id=c.id这样是不行的,这样只会把ID相同的记录查出来,但是我的不同的呢?
x.id,a.a1,a.a2,a.a3,
b.b1,b.b2,b.b3,
c.c1,c.c2,c.c3
from
(select id from a1
union
select id from a2
union
select id from a3) x,
a,b,c
where
x.id=a.id and x.id=b.id and x.id=c.id