oracle行转列、列转行总结

1.行转列

（1）decode实现

SELECT t_year,
MAX(DECODE(t_month,‘1月’,t_value)) AS 一月,
MAX(DECODE(t_month,‘2月’,t_value)) AS 二月,
MAX(DECODE(t_month,‘3月’,t_value)) AS 三月,
MAX(DECODE(t_month,‘4月’,t_value)) AS 四月
FROM a_testtable WHERE t_month IN(‘1月’,‘2月’,‘3月’,‘4月’)
GROUP BY t_year;

（2）case when实现

SELECT t_year,
MAX(CASE t_month WHEN ‘1月’ THEN t_value END) AS 一月,
MAX(CASE t_month WHEN ‘2月’ THEN t_value END) AS 二月,
MAX(CASE t_month WHEN ‘3月’ THEN t_value END) AS 三月,
MAX(CASE t_month WHEN ‘4月’ THEN t_value END) AS 四月
FROM a_testtable WHERE t_month IN(‘1月’,‘2月’,‘3月’,‘4月’)
GROUP BY t_year;

（3）pivot函数

SELECT * FROM a_testtable
PIVOT(SUM(t_value) FOR t_month IN(‘1月’ AS 一月,‘2月’ AS 二月,‘3月’ AS 三月,‘4月’ AS 四月));

SELECT * FROM
(SELECT t_year AS ye,t_month AS mon,t_value AS val FROM a_testtable) a
PIVOT(SUM(val) FOR mon IN(‘1月’ AS 一月,‘2月’ AS 二月,‘3月’ AS 三月,‘4月’ AS 四月));

2列转行

准备表及数据

（1）decode实现

SELECT t_year,
DECODE(lvl,1,‘1月’,2,‘2月’,3,‘3月’,4,‘4月’) AS t_month,
DECODE(lvl,1,one_m,2,two_m,3,tree_m,4,four_m) AS t_qty
FROM b_testtable,(SELECT LEVEL lvl FROM dual CONNECT BY LEVEL<=4)
ORDER BY t_year,t_month;

（2）case when实现

SELECT t_year,
CASE lvl WHEN 1 THEN ‘1月’
WHEN 2 THEN ‘2月’
WHEN 3 THEN ‘3月’
WHEN 4 THEN ‘4月’
END AS t_month,
CASE lvl WHEN 1 THEN one_m
WHEN 2 THEN two_m
WHEN 3 THEN tree_m
WHEN 4 THEN four_m
END AS t_qty
FROM b_testtable,(SELECT LEVEL lvl FROM dual CONNECT BY LEVEL<=4)
ORDER BY t_year,t_month;

（3）unpivot函数实现

SELECT * FROM b_testtable
UNPIVOT(t_qty FOR t_month IN(one_m AS ‘1月’,two_m AS ‘2月’,tree_m AS ‘3月’,four_m AS ‘4月’))
ORDER BY t_year,t_month;