选择两列：多个视图，相同条件

Question

我使用多个视图使用子查询和联合获取两列，我想减少执行时间。

select a.empid,empname from 
(select empid,empname from india_emp where deptno <> 10
union
select empid,empname from us_emp where deptno <> 10
union
select empid,empname from uk_emp where deptno <> 10
union
select empid,empname from uae_emp where deptno <> 10
union
select empid,empname from brazl_emp where deptno <> 10
union
select empid,empname from chine_emp where deptno <> 10
union
select empid,empname  from jpn_emp where deptno in (54,256,362,9879,24,46)
)a
where a.empid NOT IN(105,202,11,45,695,646,726,8465,965,56,646,689,446)
order by 2

Answer 1

将所有Union更改为Union All，这样便宜。

像这样：

SELECT a.empid,empname FROM 
(SELECT empid,empname FROM india_emp WHERE deptno <> 10
UNION ALL
SELECT empid,empname FROM us_emp WHERE deptno <> 10
UNION ALL
SELECT empid,empname FROM uk_emp WHERE deptno <> 10
UNION ALL
SELECT empid,empname FROM uae_emp WHERE deptno <> 10
UNION ALL
SELECT empid,empname FROM brazl_emp WHERE deptno <> 10
UNION ALL
SELECT empid,empname FROM chine_emp WHERE deptno <> 10
UNION ALL
SELECT empid,empname  FROM jpn_emp WHERE deptno in (54,256,362,9879,24,46)
)a
WHERE a.empid NOT IN(105,202,11,45,695,646,726,8465,965,56,646,689,446)
ORDER BY 2

Answer 2

你可以尝试在派生表中使用empid过滤器吗？

select a.empid,empname from 
(select empid,empname from india_emp where deptno <> 10 and empid NOT IN(105,202,11,45,695,646,726,8465,965,56,646,689,446)
union
select empid,empname from us_emp where deptno <> 10 and empid NOT IN(105,202,11,45,695,646,726,8465,965,56,646,689,446)
union
select empid,empname from uk_emp where deptno <> 10 and empid NOT IN(105,202,11,45,695,646,726,8465,965,56,646,689,446)
union
select empid,empname from uae_emp where deptno <> 10 and empid NOT IN(105,202,11,45,695,646,726,8465,965,56,646,689,446)
union
select empid,empname from brazl_emp where deptno <> 10 and empid NOT IN(105,202,11,45,695,646,726,8465,965,56,646,689,446)
union
select empid,empname from chine_emp where deptno <> 10 and empid NOT IN(105,202,11,45,695,646,726,8465,965,56,646,689,446)
union
select empid,empname  from jpn_emp where deptno in (54,256,362,9879,24,46)
)a
where 
order by 2