Question

我的桌子 - 学生的形式是

               Student    Subject1   Subject2
               A          123         1
               B                      4
               C          122

我想获取学生的所有非空记录以及列名注意：只应显示非空记录

所以当我查询学生A时，我应该

          Subject1 123               
          Subject2 1

当我查询学生B时，我应该

          Subject2 4

当我查询学生C时，我应该得到 Subject1 122

我想动态生成列名。谢谢你的帮助！

Answer 1

这可以按照以下方式完成 -

SELECT * 
FROM 
(
    WITH A AS
    (
        SELECT 'A' AS STUDENT,  123 AS SUBJECT1, 1 AS SUBJECT2 FROM DUAL
        UNION
        SELECT 'B' AS STUDENT,  NULL AS SUBJECT1, 4 AS SUBJECT2 FROM DUAL
        UNION
        SELECT 'C' AS STUDENT,  122 AS SUBJECT1, NULL AS SUBJECT2 FROM DUAL
    )
    SELECT * 
    FROM 
        A
    UNPIVOT 
        (
            MARKS FOR SUBJECT IN (SUBJECT1, SUBJECT2)
        )
) 
WHERE 
    STUDENT = 'A';

输出 -

STUDENT,SUBJECT,MARKS
A,SUBJECT1,123
A,SUBJECT2,1

使用SQL中的列名获取非null值

1 个答案: