1. Prepare data: REST table
-- 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. Query data
3. Row to column
Method 1: Use case when then method
case condition
when value 1 then return value 1
when value 2 then return value 2
..........
else default value
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 another way:
case when condition = value 1 then return value 1
case when condition = value 1 then return value 1
else default value
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 The result is:
Method 2: Use the decode function
decode function: DECODE(condition, value 1, return value 1, value 2, return value 2, value 3, return value 3, . . . else default value)
Meaning: if condition = value 1 then return value 1 elsif condition = value 2 then return value 2 else (default value) 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 The result is the same as method 1
Method 3: Use the pivot function
pivot
(
<aggregation function> (column to be aggregated)
for <column to be converted> in (column value to be converted as column name to be converted to)
)
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
)
);The result is: This result will find that if the data is empty and no value is assigned to 0
The following method solves the problem of turning null into 0
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
)
);The result is the same as method 1:
4. Column to row
Add the unpivot function to the original sql statement of the above pivot method to convert the columns into rows. In the unpivot function, amount: indicates the data converted from columns to rows
month: Indicates the column name after converting from column to row
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));
The result is:
5. Directly use the unpivot function -- column transfer
Prepare data: TEST table
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');
Query data
column to row sql
SELECT
*
FROM TEST
unpivot ( amount for month in(JAN,FEB,MAR,APR,MAY,JUN,JUL,AUG,SEP,OCT,NOV,DEC));The result is:
