1、准备数据：REST表

-- 创建表REST
CREATE TABLE REST ("ID" NUMBER,"AMOUNT" NUMBER(19,0),"MONTH" VARCHAR2(255 BYTE)
);--执行添加数据语句
INSERT INTO "CERPAWCSADM"."REST" VALUES ('1', '100', 'Jan');
INSERT INTO "CERPAWCSADM"."REST" VALUES ('1', '100', 'Feb');
INSERT INTO "CERPAWCSADM"."REST" VALUES ('1', '66', 'Mar');
INSERT INTO "CERPAWCSADM"."REST" VALUES ('1', '77', 'Jun');
INSERT INTO "CERPAWCSADM"."REST" VALUES ('1', '88', 'Dec');
INSERT INTO "CERPAWCSADM"."REST" VALUES ('1', '12', 'Aug');
INSERT INTO "CERPAWCSADM"."REST" VALUES ('2', '22', 'Feb');
INSERT INTO "CERPAWCSADM"."REST" VALUES ('2', '33', 'Apr');
INSERT INTO "CERPAWCSADM"."REST" VALUES ('2', '232', 'Jul');
INSERT INTO "CERPAWCSADM"."REST" VALUES ('2', '43', 'Sep');
INSERT INTO "CERPAWCSADM"."REST" VALUES ('2', '544', 'Oct');
INSERT INTO "CERPAWCSADM"."REST" VALUES ('2', '65', 'Nov');

2、查询数据

 3、行转列

方式1：使用 case when  then方式

case 条件

when 值1 then 返回值1

when 值2 then 返回值2

..........

else 默认值

end

-- 使用case when 方式
SELECTid,sum( CASE month WHEN 'Jan' THEN amount ELSE 0 END ) AS Jan_amount,sum( CASE month WHEN 'Feb' THEN amount ELSE 0 END ) AS Feb_amount,sum( CASE month WHEN 'Mar' THEN amount ELSE 0 END ) AS Mar_amount,sum( CASE month WHEN 'Apr' THEN amount ELSE 0 END ) AS Apr_amount,sum( CASE month WHEN 'May' THEN amount ELSE 0 END ) AS May_amount,sum( CASE month WHEN 'Jun' THEN amount ELSE 0 END ) AS Jun_amount,sum( CASE month WHEN 'Jul' THEN amount ELSE 0 END ) AS Jul_amount,sum( CASE month WHEN 'Aug' THEN amount ELSE 0 END ) AS Aug_amount,sum( CASE month WHEN 'Sep' THEN amount ELSE 0 END ) AS Sep_amount,sum( CASE month WHEN 'Oct' THEN amount ELSE 0 END ) AS Oct_amount,sum( CASE month WHEN 'Nov' THEN amount ELSE 0 END ) AS Nov_amount,sum( CASE month WHEN 'Dec' THEN amount ELSE 0 END ) AS Dec_amount 
FROMREST 
GROUP BYid 

case when 另一种方式：

        case when 条件 = 值1 then 返回值1 

        case when 条件 = 值1 then 返回值1 

        else 默认值

        end

	SELECTid,sum( CASE  WHEN month ='Jan' THEN amount ELSE 0 END ) AS Jan_amount,sum( CASE  WHEN month = 'Feb' THEN amount ELSE 0 END ) AS Feb_amount,sum( CASE  WHEN month = 'Mar' THEN amount ELSE 0 END ) AS Mar_amount,sum( CASE  WHEN month = 'Apr' THEN amount ELSE 0 END ) AS Apr_amount,sum( CASE  WHEN month = 'May' THEN amount ELSE 0 END ) AS May_amount,sum( CASE  WHEN month = 'Jun' THEN amount ELSE 0 END ) AS Jun_amount,sum( CASE  WHEN month = 'Jul' THEN amount ELSE 0 END ) AS Jul_amount,sum( CASE  WHEN month = 'Aug' THEN amount ELSE 0 END ) AS Aug_amount,sum( CASE  WHEN month = 'Sep' THEN amount ELSE 0 END ) AS Sep_amount,sum( CASE  WHEN month = 'Oct' THEN amount ELSE 0 END ) AS Oct_amount,sum( CASE  WHEN month = 'Nov' THEN amount ELSE 0 END ) AS Nov_amount,sum( CASE  WHEN month = 'Dec' THEN amount ELSE 0 END ) AS Dec_amount 
FROMREST 
GROUP BYid 

结果为：

方式2： 使用 decode函数

decode函数： DECODE(条件, 值1, 返回值1, 值2,返回值2, 值3,返回值3, . . . else 缺省值)

含义：if 条件 = 值1 then 返回值1 elsif 条件 = 值2 then 返回值2  else (缺省值) endif

--	使用decode函数
SELECTid,sum( decode( month, 'Jan', amount, 0 ) ) Jan_amount,sum( decode( month, 'Feb', amount, 0 ) ) Feb_amount,sum( decode( month, 'Mar', amount, 0 ) ) Mar_amount,sum( decode( month, 'Apr', amount, 0 ) ) Apr_amount,sum( decode( month, 'May', amount, 0 ) ) May_amount,sum( decode( month, 'Jun', amount, 0 ) ) Jun_amount,sum( decode( month, 'Jul', amount, 0 ) ) Jul_amount,sum( decode( month, 'Aug', amount, 0 ) ) Aug_amount,sum( decode( month, 'Sep', amount, 0 ) ) Sep_amount,sum( decode( month, 'Oct', amount, 0 ) ) Oct_amount,sum( decode( month, 'Nov', amount, 0 ) ) Nov_amount,sum( decode( month, 'Dec', amount, 0 ) ) Dec_amount 
FROMREST 
GROUP BYid 

结果和方式1一样

方式3：使用pivot函数

pivot
(
<聚合函数>(要聚合的列)
for <要转换的列> in (要转换的列值 as 要转换成的列名)
) 

SELECT* 
FROMREST pivot (SUM(amount) FOR month IN ('Jan' AS Jan_amount,'Feb' AS Feb_amount,'Mar' AS Mar_amount,'Apr' AS Apr_amount,'May' AS May_amount,'Jun' AS Jun_amount,'Jul' AS Jul_amount,'Aug' AS Aug_amount,'Sep' AS Sep_amount,'Oct' AS Oct_amount,'Nov' AS Nov_amount,'Dec' AS Dec_amount ) );

结果为：这个结果会发现，如果数据为空没有赋值为0

 下面这个方法解决null 转为0 问题

SELECTNVl(Jan_amount,0) Jan_amount,NVl(Feb_amount,0) Feb_amount,NVl(Mar_amount,0) Mar_amount,NVl(Apr_amount,0) Apr_amount,NVl(May_amount,0) May_amount,NVl(Jun_amount,0) Jun_amount,NVl(Jul_amount,0) Jul_amount,NVl(Aug_amount,0) Aug_amount,NVl(Sep_amount,0) Sep_amount,NVl(Oct_amount,0) Oct_amount,NVl(Nov_amount,0) Nov_amount,NVl(Dec_amount,0) Dec_amount
FROMREST pivot (SUM(amount) FOR month IN ('Jan' AS Jan_amount,'Feb' AS Feb_amount,'Mar' AS Mar_amount,'Apr' AS Apr_amount,'May' AS May_amount,'Jun' AS Jun_amount,'Jul' AS Jul_amount,'Aug' AS Aug_amount,'Sep' AS Sep_amount,'Oct' AS Oct_amount,'Nov' AS Nov_amount,'Dec' AS Dec_amount ) );

结果和方式1一样：

4、列转行

在上述pivot 方法的原sql语句上再加上unpivot函数，将列再转为行，在unpivot函数中，amount：表示由列转换为行后的数据

month：表示由列转换为行后的列名

select * from REST
pivot (sum(amount) for month in ('Jan' AS Jan_amount,'Feb' AS Feb_amount,'Mar' AS Mar_amount,'Apr' AS Apr_amount,'May' AS May_amount,'Jun' AS Jun_amount,'Jul' AS Jul_amount,'Aug' AS Aug_amount,'Sep' AS Sep_amount,'Oct' AS Oct_amount,'Nov' AS Nov_amount,'Dec' AS Dec_amount 
))
unpivot ( amount for month in(Jan_amount,Feb_amount,Mar_amount,Apr_amount,May_amount,Jun_amount,Jul_amount,Aug_amount,Sep_amount,Oct_amount,Nov_amount,Dec_amount));

结果为：

5、直接使用unpivot函数 --列转行

准备数据：TEST表

CREATE TABLE TEST ("ID" NUMBER(12,0) NOT NULL,"JAN" VARCHAR2(255 BYTE),"FEB" VARCHAR2(255 BYTE),"MAR" VARCHAR2(255 BYTE),"APR" VARCHAR2(255 BYTE),"MAY" VARCHAR2(255 BYTE),"JUN" VARCHAR2(255 BYTE),"JUL" VARCHAR2(255 BYTE),"AUG" VARCHAR2(255 BYTE),"SEP" VARCHAR2(255 BYTE),"OCT" VARCHAR2(255 BYTE),"NOV" VARCHAR2(255 BYTE),"DEC" VARCHAR2(255 BYTE)
);
-- 插入数据
INSERT INTO "CERPAWCSADM"."TEST" VALUES ('1', '33', '2', '3', '4', '5', '6', '7', '8', '9', '99', '8', '6');
INSERT INTO "CERPAWCSADM"."TEST" VALUES ('2', '22', '3', '4', '6', '5', '7', '0', '7', '22', '21', '343', '76');
INSERT INTO "CERPAWCSADM"."TEST" VALUES ('3', '88', '3', '4', '5', '7', '9', '7', '2', '2', '231', '56', '78');

查询出的数据

列转行sql

SELECT* 
FROM TESTunpivot ( amount for month in(JAN,FEB,MAR,APR,MAY,JUN,JUL,AUG,SEP,OCT,NOV,DEC));

 结果为：