select tabla.*,tablb.*
from tabla,select tablc.* ,(from tablc where tablc.d='xxx') tablb
where tabla.a=tablb.a(+) and
tabla.b=tablb.b(+) and
tabla.c='xxx'
这样的SQL文怎么建索引
from tabla,select tablc.* ,(from tablc where tablc.d='xxx') tablb
where tabla.a=tablb.a(+) and
tabla.b=tablb.b(+) and
tabla.c='xxx'
这样的SQL文怎么建索引
tablc还有一个检索条件
主表也有检索条件tabla.c='xxx' 帮一把,同志们
改过了
select tabla.*,tablb.*
from tabla,(select tablc.* from tablc where tablc.d='xxx') tablb
where tabla.a=tablb.a(+) and
tabla.b=tablb.b(+) and
tabla.c='xxx'
select tabla.*,tablc.* from tabla,tablc where
tabla.c='xxx'
and tablc.d='xxx'
and tabla.a=tablc.a(+)
and tabla.b=tablc.b(+)
在tabla.c,tablc.d中创建B树索引在tabla,tablc的a b 列上建立聚簇
tablc.d='xxx'
能过滤25%的数据tablc.d='xxx' 就不好说了
select tabla.*,tablc.* from tabla,tablc where
tabla.c='xxx'
and tablc.d='xxx'
and tabla.a=tablc.a(+)
and tabla.b=tablc.b(+) 因为是使用外联
这样做tabla表的数据不能被全部选出