我有桌子
dn_table ~ 10_000 rows
| DN |
--------
| 1234 |
| 1235 |
| .... |
sr_table ~ 1m rows
| SR |
--------
| 2345 |
| 2346 |
| .... |
我坚持对他们进行横向连接查询。它具有极差的性能,一些查询运行数小时取决于数据集大小,同时选择限制。
select
*
from (
select
"alias1"."DN",
"alias2"."SR"
from (
select "alias1"."DN"
from "dn_table" as "alias1"
) as "alias1" left outer join lateral (
select *
from "sr_table" as "alias2"
where "alias1"."DN" = "alias2"."SR"
limit 1
) as "alias2" on true
) as "alias"
我尝试为它们使用相关子查询,但它给我带来了我没想到的结果。
提前致谢!