使用分析函数进行行列转换

比如查询scott.emp表的用户SAL排序信息，可以使用如下查询：

SQL> SELECT deptno, ename,

  2         ROW_NUMBER () OVER (PARTITION BY deptno ORDER BY sal DESC) seq

  3    FROM emp;



    DEPTNO ENAME             SEQ

---------- ---------- ----------

        10 KING                1

        10 CLARK               2

        10 MILLER              3

        20 SCOTT               1

        20 FORD                2

        20 JONES               3

        20 ADAMS               4

        20 SMITH               5

        30 BLAKE               1

        30 ALLEN               2

        30 TURNER              3

        30 WARD                4

        30 MARTIN              5

        30 JAMES               6



14 rows selected.

再结合其他函数进行一下行列转换:

SQL> select deptno,

  2  max(decode(seq,1,ename,null)) highest,

  3  max(decode(seq,2,ename,null)) second,

  4  max(decode(seq,3,ename,null)) third

  5  from (

  6  select deptno,ename,

  7  row_number() over

  8  (partition by deptno order by sal desc) seq

  9  from emp)

 10  where seq <=3 group by deptno

 11  /



    DEPTNO HIGHEST    SECOND     THIRD

---------- ---------- ---------- ----------

        10 KING       CLARK      MILLER

        20 SCOTT      FORD       JONES

        30 BLAKE      ALLEN      TURNER

这个结果基本上还是差强人意的。