------------SQL 1:出结果需要2分多钟----------------
表达式A
where ( h.A_NUM2 = 'S'
OR h.A_NUM2 in
( SELECT to_char(customer.CUSTOMERID)
FROM customer )
)
-------------------------------------------------------------SQL 2:马上能出结果-------------------
表达式A
where h.A_NUM2 in
(SELECT to_char(customer.CUSTOMERID)
FROM customer)
union all
表达式A
where h.A_NUM2 = 'S'
-------------------------------------------------为什么这样?
表达式A
where ( h.A_NUM2 = 'S'
OR h.A_NUM2 in
( SELECT to_char(customer.CUSTOMERID)
FROM customer )
)
-------------------------------------------------------------SQL 2:马上能出结果-------------------
表达式A
where h.A_NUM2 in
(SELECT to_char(customer.CUSTOMERID)
FROM customer)
union all
表达式A
where h.A_NUM2 = 'S'
-------------------------------------------------为什么这样?
SQL2 用上了索引
所以,考虑将语句修改
select ..
where ( h.A_NUM2 = 'S '
OR h.A_NUM2 in
( SELECT to_char(customer.CUSTOMERID)
FROM customer )
)
union all
select
where h.A_NUM2 = 'S '
所以,考虑将语句修改
select ..
where h.A_NUM2 in
( SELECT to_char(customer.CUSTOMERID)
FROM customer )
union all
select
where h.A_NUM2 = 'S '