即使在IN子句中找不到列也将其获取为NULL

Question

这是我的查询：

 SELECT numit,id FROM pecas where numit in (40363, 40366, 40310, 40320, 40362, 40364, 40385, 40415);

结果是：

numit | id
40363   50
40362   65

我想在IN子句中获取所有'numit'值，如果找不到对应的ID，则将'id'列替换为NULL。

numit | id
40362   65
40363   50
40366   NULL
40310   NULL
40320   NULL
40364   NULL
40385   NULL
40415   NULL

Answer 1

这是我到目前为止最简单的方法。它需要使用IN子句中的所有值创建一个伪表，以便将它们包含在结果中。当然，如果可以将IN子句值作为同一张或另一张表中的行的列表来提取，则可以简化它（但如果是这种情况，则需要编辑问题）。

SELECT p.numit, p.id FROM pecas p WHERE p.numit IN (40363, 40366, 40310, 40320, 40362, 40364, 40385, 40415)
UNION
  SELECT * FROM
    ( SELECT 40363 AS numit, NULL AS id
      UNION
      SELECT 40366 AS numit, NULL AS id
      UNION
      SELECT 40310 AS numit, NULL AS id
      UNION
      SELECT 40320 AS numit, NULL AS id
      UNION
      SELECT 40362 AS numit, NULL AS id
      UNION
      SELECT 40364 AS numit, NULL AS id
      UNION
      SELECT 40385 AS numit, NULL AS id
      UNION
      SELECT 40415 AS numit, NULL AS id
    ) t WHERE t.numit NOT IN (SELECT p2.numit FROM pecas p2 WHERE p2.numit IN (40363, 40366, 40310, 40320, 40362, 40364, 40385, 40415))

Answer 2

如果where子句中的数字数据来自其他表，则可以使用左连接。

    SELECT
    product_name,
    order_id
FROM
    production.products p
LEFT JOIN sales.order_items o ON o.product_id = p.product_id
 where o.product_id in(40363, 40366, 40310, 40320, 40362, 40364, 40385, 4041,4363, 466, 310, 1320, 4032, 40364, 440385, 41041)
ORDER BY
    order_id;

Answer 3

我想您可以先使用UNION子句组合它们，然后按如下所示获取最大ID-

SELECT numit, MAX(id)
FROM (SELECT numit,id
      FROM pecas
      WHERE numit in (SELECT itext FROM pecas)
      UNION
      SELECT itext, NULL
      FROM pecas) T
GROUP BY numit;

Answer 4

请尝试以下操作：

select numit, 
case id in (40363, 40366, 40310, 40320, 40362, 40364, 40385, 40415) then id
  else Null 
    end id
from pecas