从子查询中选择“最佳结果”？

Question

SELECT * FROM table1
WHERE col1 = ANY (
    SELECT DISTINCT col2 FROM table2
    WHERE first = 'blah'
    OR second = 'blahblah'
    OR third = 'blahblahblah' );

子查询检查三列（ first ， second ， third ）。 在此示例中，我使用ANY ，但是我希望它像这样返回：

If found `first` return `first`
else if found `second` return `second`
else if found `third` return `third`

知道我在说什么吗？ 我只能在first ， second ， third优先级中选择1行（最佳）

Answer 1

我想你想要这个：

SELECT * FROM table1
WHERE col1 = (
    SELECT col2 FROM table2
    WHERE first = 'blah'
    OR second = 'blahblah'
    OR third = 'blahblahblah'
    ORDER BY
    first = 'blah' DESC,
    second = 'blahblah' DESC,
    third = 'blahblahblah' DESC
    LIMIT 1
);

Answer 2

这是您想要的吗？

SELECT t.*, 'first'
FROM table1 t
WHERE col1 IN (SELECT col2 FROM table2 WHERE first = 'blah')
UNION ALL
SELECT t.*, 'second'
FROM table1 t
WHERE col1 IN (SELECT col2 FROM table2 WHERE first <> 'blah' AND second = 'blahblah')
UNION ALL
SELECT t.*, 'third'
FROM table1 t
WHERE col1 IN (SELECT col2 FROM table2 WHERE first <> 'blah' AND second <> 'blahblah' AND third = 'blahblahblah' );

对于每个匹配项（基于col1 ），它返回三个条件中的第一个。

Answer 3

尝试这个，

 SELECT *, COALESCE(first, second, third) as best FROM tab