与一个不同的列合并

Question

我想使用UNION连接两个视图（视图CSP多包含1列，因此如果第二个视图中的某些项不在第一个视图中，则我想在第二个中使用*），但效果很好，但是我没有重复的配置ID要么带有正确的值，要么带有*。

当csp中有值时，如何解决该问题并删除带有“ *”的行？

SELECT csp.customer_no,
       csp.contract,
       csp.customer_part_no,
       csp.configuration_id,
       csp.catalog_no
FROM customersomething csp
UNION
SELECT spc.customer_no,
       spc.contract,
       spc.customer_part_no,
       '*' AS "configuration_id",
       spc.catalog_no
FROM
superproduct spc

+-------------+----------+-----+------------------+--------+
| customer_no | contract | ... | configuration_id |        |
+-------------+----------+-----+------------------+--------+
|          17 | whatever | ... | *                | view A |
|          17 | whatever | ... | right_one        | view B |
+-------------+----------+-----+------------------+--------+

Answer 1

首先，使用union all除非您要承担删除重复项的开销。

第二，滤除第二个。 这是使用not exists ：

SELECT csp.customer_no, csp.contract, csp.customer_part_no,
       csp.configuration_id, csp.catalog_no
FROM customersomething csp
UNION ALL
SELECT spc.customer_no, spc.contract, spc.customer_part_no,
       '*' AS "configuration_id", spc.catalog_no
FROM superproduct spc
WHERE NOT EXISTS (SELECT 1
                  FROM customersomething csp
                  WHERE scp.customer_no = spc.customer_no
                 );

Answer 2

您可以使用此查询，

SELECT spc.customer_no,
   spc.contract,
   spc.customer_part_no,
   csp.configuration_id,
   spc.catalog_no FROM superproduct spc
   LEFT JOIN customersomething csp ON spc.customer_no = csp.customer_no
   UNION ALL
   SELECT csp.customer_no,
   csp.contract,
   csp.customer_part_no,
   csp.configuration_id,
   csp.catalog_no
   FROM customersomething csp
   LEFT JOIN  superproduct spc ON spc.customer_no = csp.customer_no AND spc.customer_no IS NULL