MySQL将行透视为动态列数
假设我有三个不同的MySQL表: 表MySQL将行透视为动态列数,mysql,sql,pivot,Mysql,Sql,Pivot,假设我有三个不同的MySQL表: 表产品: id | name 1 Product A 2 Product B id | name 1 Partner A 2 Partner B 表合作伙伴: id | name 1 Product A 2 Product B id | name 1 Partner A 2 Partner B 表销售额: partners_id | products_id 1 2
产品
:
id | name
1 Product A
2 Product B
id | name
1 Partner A
2 Partner B
表合作伙伴
:
id | name
1 Product A
2 Product B
id | name
1 Partner A
2 Partner B
表销售额
:
partners_id | products_id
1 2
2 5
1 5
1 3
1 4
1 5
2 2
2 4
2 3
1 1
我想得到一个表,其中合作伙伴在行中,产品在列中。到目前为止,我能够得到如下输出:
name | name | COUNT( * )
Partner A Product A 1
Partner A Product B 1
Partner A Product C 1
Partner A Product D 1
Partner A Product E 2
Partner B Product B 1
Partner B Product C 1
Partner B Product D 1
Partner B Product E 1
SET @sql = NULL;
SELECT
GROUP_CONCAT(DISTINCT
CONCAT(
'count(case when Product_Name = ''',
Product_Name,
''' then 1 end) AS ',
replace(Product_Name, ' ', '')
)
) INTO @sql
from products;
SET @sql = CONCAT('SELECT pt.partner_name, ', @sql, ' from partners pt
left join sales s
on pt.part_id = s.partner_id
left join products pd
on s.product_id = pd.prod_id
group by pt.partner_name');
PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
使用此查询:
SELECT partners.name, products.name, COUNT( * )
FROM sales
JOIN products ON sales.products_id = products.id
JOIN partners ON sales.partners_id = partners.id
GROUP BY sales.partners_id, sales.products_id
LIMIT 0 , 30
但我想换成这样:
partner_name | Product A | Product B | Product C | Product D | Product E
Partner A 1 1 1 1 2
Partner B 0 1 1 1 1
问题是,我无法说出我将拥有多少产品,因此列号需要根据products表中的行动态更改
这个非常好的答案似乎对mysql不起作用:不幸的是,mysql没有一个基本上就是您要做的
PIVOT
函数。因此,您需要将聚合函数与CASE
语句一起使用:
select pt.partner_name,
count(case when pd.product_name = 'Product A' THEN 1 END) ProductA,
count(case when pd.product_name = 'Product B' THEN 1 END) ProductB,
count(case when pd.product_name = 'Product C' THEN 1 END) ProductC,
count(case when pd.product_name = 'Product D' THEN 1 END) ProductD,
count(case when pd.product_name = 'Product E' THEN 1 END) ProductE
from partners pt
left join sales s
on pt.part_id = s.partner_id
left join products pd
on s.product_id = pd.prod_id
group by pt.partner_name
看
由于您不知道产品,您可能希望动态执行此操作。这可以使用准备好的语句来完成
使用动态数据透视表(将行转换为列),您的代码如下所示:
name | name | COUNT( * )
Partner A Product A 1
Partner A Product B 1
Partner A Product C 1
Partner A Product D 1
Partner A Product E 2
Partner B Product B 1
Partner B Product C 1
Partner B Product D 1
Partner B Product E 1
SET @sql = NULL;
SELECT
GROUP_CONCAT(DISTINCT
CONCAT(
'count(case when Product_Name = ''',
Product_Name,
''' then 1 end) AS ',
replace(Product_Name, ' ', '')
)
) INTO @sql
from products;
SET @sql = CONCAT('SELECT pt.partner_name, ', @sql, ' from partners pt
left join sales s
on pt.part_id = s.partner_id
left join products pd
on s.product_id = pd.prod_id
group by pt.partner_name');
PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
看
可能值得注意的是,
GROUP\u CONCAT
默认限制为1024字节。您可以通过在整个过程中将其设置得更高来解决此问题,即。SET@@group\u concat\u max\u len=32000代码>结尾关于“max_len”的评论是一个救星!感谢您的提示。如果您正在寻找更多动态pivot查询,请检查以下内容:如果partners pt的产品名称为ProductA'),会发生什么情况;截断合作伙伴代码>@avatarofhope2这是一个问题还是一种暗示?如果这提供了一个注入角度,那么什么是正确的处理方法?请参阅链接以获取多个建议。@BhavinPokiya,这是您提供的MS SQL Server链接,而它被标记为MySQL。