使用 PostgreSQL 9.3 的动态数据透视查询
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Dynamic pivot query using PostgreSQL 9.3
提问by MAK
I have a table named as Product:
我有一个名为的表Product：
create table product (
ProductNumber varchar(10),
ProductName varchar(10),
SalesQuantity int,
Salescountry varchar(10)
);
Sample values:
示例值：
insert into product values
('P1', 'PenDrive', 50, 'US')
, ('P2', 'Mouse', 100, 'UK')
, ('P3', 'KeyBoard', 250, 'US')
, ('P1', 'PenDrive', 300, 'US')
, ('P2', 'Mouse', 450, 'UK')
, ('P5', 'Dvd', 50, 'UAE');
I want to generate the Salescountry'snames dynamically and show the sum of SalesQuantitysale in that Country.
我想Salescountry's动态生成名称并显示该SalesQuantity国家/地区的销售总额。
Expected result:
预期结果：
ProductName US UK UAE
----------------------------
PenDrive 350 0 0
Mouse 0 550 0
KeyBoard 250 0 0
Dvd 0 0 50
I did it using SQL Server 2008 R2:
我使用 SQL Server 2008 R2 做到了：
DECLARE @cols AS NVARCHAR(MAX),
@query AS NVARCHAR(MAX);
SET @cols = STUFF((SELECT distinct ',' + QUOTENAME(SalesCountry)
FROM Product
FOR XML PATH(''), TYPE
).value('.', 'NVARCHAR(MAX)')
,1,1,'')
set @query = 'SELECT ProductName, ' + @cols + ' from
(
select ProductName
, SalesQuantity as q
, Salescountry
from Product
) x
pivot
(
SUM(q)
for Salescountry in (' + @cols + ')
) p '
PRINT(@query);
execute(@query);
How to achieve this in Postgres?
如何在 Postgres 中实现这一点？
采纳答案by Erwin Brandstetter
SELECT *
FROM crosstab (
'SELECT ProductNumber, ProductName, Salescountry, SalesQuantity
FROM product
ORDER BY 1'
, $$SELECT unnest('{US,UK,UAE1}'::varchar[])$$
) AS ct (
"ProductNumber" varchar
, "ProductName" varchar
, "US" int
, "UK" int
, "UAE1" int);
Detailed explanation:
详细解释：
Completely dynamic query for varying number of distinct Salescountry?
不同数量的不同的完全动态查询Salescountry？
回答by Peter
While it's a two step process, this method will create a pivot with dynamic columns, without the need to specify the result set and without creating temp tables.
虽然这是一个两步过程，但此方法将创建一个具有动态列的数据透视表，无需指定结果集，也无需创建临时表。
First we define a function that creates a dynamically prepared statement:
首先我们定义一个创建动态准备语句的函数：
CREATE OR REPLACE FUNCTION flowms.pivotcode_sql(
tablename character varying,
rowc character varying,
colc character varying,
cellc character varying,
celldatatype character varying)
RETURNS character varying
LANGUAGE 'plpgsql'
COST 100
VOLATILE
AS $BODY$
declare
dynsql1 varchar;
dynsql2 varchar;
columnlist varchar;
begin
-- 1. retrieve list of column names.
dynsql1 = 'select string_agg(distinct ''"''||'||colc||'||''" '||celldatatype||''','','' order by ''"''||'||colc||'||''" '||celldatatype||''') from '||tablename||';';
execute dynsql1 into columnlist;
-- 2. set up the crosstab query
--tablename = REPLACE(text, ''', E'\"')
dynsql2 = 'prepare crosstab_stmt as select * from crosstab (
''select '||rowc||','||colc||','||cellc||' from '||replace(tablename, chr(39),E'\'\'')||' group by 1,2 order by 1,2'',
''select distinct '||colc||' from '||replace(tablename, chr(39),E'\'\'')||' order by 1''
)
as newtable (
'||rowc||' varchar,'||columnlist||'
);';
deallocate all;
execute dynsql2;
return dynsql2;
end
$BODY$;
You can now call the function
您现在可以调用该函数
select pivotcode_sql('tablename', 'rowfield', 'columnfield', 'sum(value)', 'integer');
which will create the prepared statement. Next you can execute the prepared statement:
这将创建准备好的语句。接下来你可以执行准备好的语句：
execute crosstab_stmt;
