Question

我有两个表service_category和category_mapping。我想显示特定类别中列出的公司类别和数量

Table service_category:

id    cattegory          mappingid
1     Construction          cc
2     InteriorDesign        idn
3     TechnicalWork         tw
4     MarineConstruction    mc

Table category_mapping:

id    companyid        cc    idn    tw   mc
1         4            Y      Y     N    N
2         5            N      Y     N    Y
3         6            N      N     N    Y
4         7            Y      N     N    N

类似这样的事情

SELECT  sc.*,(select count(*) from category_mapping where `XYZ`='Y' ) as companycount  FROM  service_category as sc

任何人都可以帮助我吗？

Answer 1

如果有更多类别，这将仅对提及的类别有用..

select id, cattegory ,mappingid ,(select  count(*) from category_mapping  where cc='Y') as count
from 
service_category
where mappingid='CC'
union 
select id, cattegory ,mappingid ,(select  count(*) from category_mapping  where idn='Y') as count
from 
service_category
where mappingid='idn'

连接表，其中一个表中的字段值是另一个表中的列名

1 个答案: