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
SELECT
id,
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
FROM
REST
GROUP BY
id
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
SELECT
id,
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
FROM
REST
GROUP BY
id 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
SELECT
id,
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
FROM
REST
GROUP BY
id 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
*
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
)
);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
SELECT
NVl(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
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
)
);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 TEST
unpivot ( amount for month in(JAN,FEB,MAR,APR,MAY,JUN,JUL,AUG,SEP,OCT,NOV,DEC));结果为：
