如何将几行合并为一行？

Question

我怎样才能获得

column1  column2   column3
value1   value2    value3

来自

column1  column2   column3
value1   null      null
null     value2    null
null     null      value3

Answer 1

你应该用这个：

SELECT T1.column1, T2.column2, T3.column3 FROM test1 T1
LEFT JOIN test1 T2 ON T2.column2 is not null
LEFT JOIN test1 T3 ON T3.column3 is not null
WHERE T1.column1 is not null