MySQL Union - NULL为var？

Question

查看此查询示例：

(SELECT fistName, middleName, lastName
FROM a)
UNION
(SELECT fistName, NULL as middleName, lastName
FROM b)

这样可以正常工作吗？表b根本没有中间名列...我想如果它不能正常运行，我总是可以试试这个：

'' as middlename

...谢谢

Answer 1

当然可行。此外，您不需要使用as middleName

(SELECT fistName, middleName, lastName
FROM a)
UNION
(SELECT fistName, NULL, lastName
FROM b)