Question

oracle 中sql执行超慢几乎查询不出来

select LINKEDSTATION
from rstation t
where 1 = 1
and t.LinkedStation in
(select global_id
from bdz_app@linked bdz
where bdz.OBJ_ID in
(SELECT PZ.BDZ
FROM WHBZPZ@linked PZ
WHERE PZ.WHDW in (SELECT OBJ_ID
FROM DEPS@linked deps
where 1 = 1
START WITH OBJ_ID =
'63EBEC8E-00165'
CONNECT BY PRIOR OBJ_ID = SJBM)))

Answer 1

套这么多层，而且用到DB LINK表那当然慢了
如果只执行一次最好把DB LINK的表创建一个中间表过来
再把这几个中间表联查速度会快多了

追问

但是我只执行and t.LinkedStation in后面的sql就很快

追答

后面SQL查出来有多少个结果集？超过一千个使用exists

Answer 2

select LINKEDSTATION from rstation t
left join bdz_app b on b.OBJ_ID =t.LinkedStation
left join WHBZPZ w on b.OBJ_ID =PZ.WHDW
left join DEPS d on PZ.WHDW = d.OBJ_ID
and d.OBJ_ID =' '63EBEC8E-00165''

Answer 3

你写太多重的select了，可以考虑数据表连接查询

Answer 4

的萨达撒的撒