mysql union选择table1 field3 = table2 field5的位置

Question

我从mysql开始，我不知道如何解决这样的问题：

SELECT 
  table1.col1 AS A,
  table1.col3 As B
UNION
  table2.col2 AS C,
  table2.col5 AS D
WHERE
  table1.col4 = table2.col6

/*expected*/
A B C D

Answer 1

为什么不说：

SELECT 
  table1.col1 AS A,
  table1.col3 As B,
  table2.col2 AS C,
  table2.col5 AS D
FROM TABLE1
INNER JOIN Table2 on TABLE2.col6=TABLE1.col4