如何在Postgresql中显示特定状态下每个客户和产品组合的最大数量?
我最近才开始学习Postgresql。 我有一张名为“销售”的桌子:如何在Postgresql中显示特定状态下每个客户和产品组合的最大数量?,postgresql,join,group-by,row-number,case-when,Postgresql,Join,Group By,Row Number,Case When,我最近才开始学习Postgresql。 我有一张名为“销售”的桌子: create table sales ( cust varchar(20), prod varchar(20), day integer, month integer, year integer, state char(2), quant integer ) inser
create table sales
(
cust varchar(20),
prod varchar(20),
day integer,
month integer,
year integer,
state char(2),
quant integer
)
insert into sales values ('Bloom', 'Pepsi', 2, 12, 2001, 'NY', 4232);
insert into sales values ('Knuth', 'Bread', 23, 5, 2005, 'PA', 4167);
insert into sales values ('Emily', 'Pepsi', 22, 1, 2006, 'CT', 4404);
insert into sales values ('Emily', 'Fruits', 11, 1, 2000, 'NJ', 4369);
insert into sales values ('Helen', 'Milk', 7, 11, 2006, 'CT', 210);
......
看起来是这样的:
总共有500行
现在,我想使用查询来实现这一点:
对于客户和产品的每个组合,输出的最大销售量为
NJ和CT的NY和最低销售数量在3个单独的列中。像第一个
报告,显示相应的日期(即最大和最小销售额的日期
数量)。此外,对于CT和NJ,仅包括2000年之后发生的销售;
对于纽约,包括所有销售。
应该是这样的:
我尝试了以下查询:
SELECT
cust customer,
prod product,
MAX(CASE WHEN rn3 = 1 THEN quant END) NY_MAX,
MAX(CASE WHEN rn3 = 1 THEN TO_DATE(year || '-' || month || '-' || day, 'YYYY-MM-DD') END) date,
MIN(CASE WHEN rn2 = 1 THEN quant END) NJ_MIN,
MIN(CASE WHEN rn2 = 1 THEN TO_DATE(year || '-' || month || '-' || day, 'YYYY-MM-DD') END) date,
MIN(CASE WHEN rn1 = 1 THEN quant END) CT_MIN,
MIN(CASE WHEN rn1 = 1 THEN TO_DATE(year || '-' || month || '-' || day, 'YYYY-MM-DD') END) date
FROM (
SELECT
*,
ROW_NUMBER() OVER(PARTITION BY cust, prod ORDER BY quant) rn1,
ROW_NUMBER() OVER(PARTITION BY cust, prod ORDER BY quant) rn2,
ROW_NUMBER() OVER(PARTITION BY cust, prod ORDER BY quant DESC) rn3
FROM sales
) x
WHERE rn1 = 1 OR rn2 = 1 or rn3 = 1
GROUP BY cust, prod;
结果是:
这是错误的,因为它显示了所有状态的最大数量和最小数量,而不是我想要的特定状态。我也不知道该如何处理这一年,这是我要做的问题。我们可以使用单独的CTE和日历表来处理这一问题:
WITH custprod AS (
SELECT DISTINCT cust, prod
FROM sales
),
ny_sales AS (
SELECT *, ROW_NUMBER() OVER (PARTITION BY cust, prod ORDER BY quant DESC) rn
FROM sales
WHERE state = 'NY'
),
nj_sales AS (
SELECT *, ROW_NUMBER() OVER (PARTITION BY cust, prod ORDER BY quant) rn
FROM sales
WHERE state = 'NJ'
),
ct_sales AS (
SELECT *, ROW_NUMBER() OVER (PARTITION BY cust, prod ORDER BY quant) rn
FROM sales
WHERE state = 'CT'
)
SELECT
cp.cust,
cp.prod,
nys.quant AS ny_max,
nys.year::text || '-' || nys.month::text || '-' || nys.day::text AS ny_date,
njs.quant AS nj_max,
njs.year::text || '-' || njs.month::text || '-' || njs.day::text AS nj_date,
cts.quant AS ct_max,
cts.year::text || '-' || cts.month::text || '-' || cts.day::text AS ct_date
FROM custprod cp
LEFT JOIN ny_sales nys
ON cp.cust = nys.cust AND cp.prod = nys.prod AND nys.rn = 1
LEFT JOIN nj_sales njs
ON cp.cust = njs.cust AND cp.prod = njs.prod AND njs.rn = 1
LEFT JOIN ct_sales cts
ON cp.cust = cts.cust AND cp.prod = cts.prod AND cts.rn = 1
ORDER BY
cp.cust,
cp.prod;
注意:您没有提供全面的示例数据,但上面的内容似乎在下面的演示链接中起作用
样本数据最好以格式化文本的形式呈现。有关如何创建美观表格的一些提示,请参阅。为了简单起见,我会使用
横向连接来完成此操作。感谢您的帮助!!!它也适用于我的全部数据。还有一件事,如何只包括CT和NJ在2000年后的销售额,并包括纽约的所有销售额???@WikizVito你基本上是在问一个全新的问题,你真的应该提出一个新的问题。好吧。。。但我自己已经解决了这个新问题。非常感谢你!!