SQL 匹配列

Question

假设我有这些数据。 每个有id的人，有2张优惠券1和2，按照往返的方式。 像这样：

      ID     coupon from   to
"1000003328"    "1" "TSE"   "ALA"
"1000003328"    "2" "ALA"   "TSE"
"1000009615"    "1" "CIT"   "ALA"
"1000009615"    "2" "ALA"   "IST"
"1000014040"    "1" "DEL"   "ALA"
"1000014040"    "2" "ALA"   "FRU"
"1000017533"    "1" "KBP"   "ALA"
"1000017533"    "2" "ALA"   "PEK"
"1000020561"    "1" "ALA"   "CIT"
"1000020561"    "2" "CIT"   "ALA"
"1000026798"    "1" "GUW"   "SCO"
"1000026798"    "2" "SCO"   "GUW"

是否可以仅提取男性，其中“来自”优惠券 1 列的第 1 行的数据与“至”优惠券 2 列的第 2 行匹配？ 这符合上述条件：

       ID     coupon from   to
"1000003328"    "1"  "TSE"   "ALA"
"1000003328"    "2"  "ALA"   "TSE" 

因为第 1 行列“来自”优惠券 1 (TSE) 等于第 2 行“到”优惠券 2。

感谢你！

Answer 1

随着EXISTS ：

select t.* from tablename t
where exists (
  select 1 from tablename
  where id = t.id and coupon <> t.coupon and "from" = t."to" and "to" = t."from"
)

如果从来没有from等于 to 的情况to那么您可以删除条件and coupon <> t.coupon 。
请参阅演示。
结果：

| id         | coupon | from | to  |
| ---------- | ------ | ---- | --- |
| 1000003328 | 1      | TSE  | ALA |
| 1000003328 | 2      | ALA  | TSE |
| 1000020561 | 1      | ALA  | CIT |
| 1000020561 | 2      | CIT  | ALA |
| 1000026798 | 1      | GUW  | SCO |
| 1000026798 | 2      | SCO  | GUW |

Answer 2

你特别提到了优惠券“1”和“2”，所以我会去：

select t.*
from t
where t.coupon in (1, 2) and
      exists (select 1
              from t t2
              where t2.id = t.id and
                    t2.from = t.to and
                    t2.to = t.from and
                    t2.coupon <> t.coupon
             );

请注意，对于列名， to和from是非常糟糕的选择，因为它们是SQL 关键字。