oracle 列数据转成行数据

year	m1	m2	m3	m4
1991	1.1	1.2	1.3	1.4
1992	2.1	2.2	2.3	2.4

 

SELECT YEAR
    ,
    max( CASE WHEN rk = 1 THEN average ELSE NULL END ) AS m1,
    max( CASE WHEN rk = 2 THEN average ELSE NULL END ) AS m2,
    max( CASE WHEN rk = 3 THEN average ELSE NULL END ) AS m3,
    max( CASE WHEN rk = 4 THEN average ELSE NULL END ) AS m4 
FROM
    ( SELECT row_number ( ) over ( PARTITION BY year ORDER BY average ) rk FROM input_money ) t 
GROUP BY
YEAR