在两列中合并两个具有不同值的选择语句

Question

我有两个选择语句：

SELECT '1' AS ID , 'JOHN' AS SURNAME, NULL AS FIRSTNAME
SELECT '1' AS ID,  NULL AS SURNAME, 'BLOGGS' AS FIRSTNAME

如何通过将两行合并为结果的方式在结果中获取此信息？

1 | JOHN | BLOGGS

Answer 1

你可以用做union all和聚合：

SELECT ID, MAX(SURNAME) as SURNAME, MAX(FIRSTNAME) as FIRSTNAME
FROM (SELECT '1' AS ID , 'JOHN' AS SURNAME, NULL AS FIRSTNAME
      UNION ALL
      SELECT '1' AS ID,  NULL AS SURNAME, 'BLOGGS' AS FIRSTNAME
     ) t
GROUP BY ID;