MySQL - 从两个不同的表重命名具有相同名称的选定列

Question

我从两个不同的表中选择相同的列，但想要使用select as来使它们具有不同的名称。

(SELECT letter AS letter_1, sex AS sex_1 FROM `celebs_a` LIMIT 1) 
UNION 
(SELECT letter AS letter_2, sex AS sex_2 FROM `celebs_b` LIMIT 1) 

该查询返回此：

letter_1 sex_1 
a  1 
b  1 

但是，我想它返回此：

letter_1 letter_2 sex_1 sex_2 
a  b  1  1 

我怎样才能让该查询返回的每个值作为不同的列名？谢谢。

Answer 1

SELECT MAX(letter_1) AS letter_1, MAX(sex_1) AS sex_1, 
     MAX(letter_2) AS letter_2, MAX(sex_2) AS sex_2 
FROM (
    (SELECT letter AS letter_1, '' AS letter_2, sex AS sex_1, 0 AS sex_2 
    FROM celebs_a 
    LIMIT 1) 
    UNION 
    (SELECT '' AS letter_1, letter AS letter_2, 0 AS sex_1, sex AS sex_2 
    FROM celebs_b 
    LIMIT 1) 
) AS derived_table_must_have_an_alias 

您可以轻松地扩展这个到从每个表中选择多个列。只需将0或''作为另一个表中这些列的占位符。

Answer 2

试试这个：

SELECT 
    (SELECT letter AS letter_1 FROM `celebs_a` LIMIT 1) AS letter_1, 
    (SELECT letter AS letter_2 FROM `celebs_b` LIMIT 1) AS letter_2; 

更新时间：

SELECT 
    (SELECT letter ... FROM celebs_a ...) AS letter_1, 
    (SELECT letter ... FROM celebs_b ...) AS letter_2, 
    (SELECT sex ... FROM celebs_a ...) AS sex_1, 
    (SELECT sex ... FROM celebs_b ...) AS sex_2 

或者Barmars的做法会更好（这仅运行2 SELECT查询）