Sql 用另一个表合并两个表
我有一个典型的N-M关系结构,如下所示: 两个独立的表格:Sql 用另一个表合并两个表,sql,database,join,Sql,Database,Join,我有一个典型的N-M关系结构,如下所示: 两个独立的表格: Table Client: id | name 1 | Joe 2 | Marc 及 和一个链接表,如: Table Purchase: idClient | idProduct | Paid 1 | 1 | 3000 1 | 2 | 2999 2 | 3 | 4500 2 | 1 | 1000 我想要一个生成
Table Client:
id | name
1 | Joe
2 | Marc
及
和一个链接表,如:
Table Purchase:
idClient | idProduct | Paid
1 | 1 | 3000
1 | 2 | 2999
2 | 3 | 4500
2 | 1 | 1000
我想要一个生成以下内容的查询:
client | Toyota | Ford | Fiat
Joe | 3000 | 2999 |
Marc | 1000 | | 4500
在MySQL中有什么方法可以做到这一点吗
谢谢 您正在尝试执行透视查询;有很多关于stackoverflow的例子。搜索Pivot和MySQL 例如,下面是一个使用CASE语句的示例:
就像@StuartAinsworth所说的那样,您需要执行一个Pivot查询
对于动态方法,请使用以下方法:
create table Client (
id int,
name varchar(10)
)
insert into Client values (1, 'Joe')
insert into Client values (2, 'Marc')
create table Product (
id int,
name varchar(10)
)
insert into Product values (1, 'Toyota')
insert into Product values (2, 'Ford')
insert into Product values (3, 'Fiat')
create table Purchase (
idClient int,
idProduct int,
Paid int
)
insert into Purchase values (1, 1, 3000)
insert into Purchase values (1, 2, 2999)
insert into Purchase values (2, 3, 4500)
insert into Purchase values (2, 1, 1000)
declare @cmd varchar(2048)
declare @prod varchar(10), @count int, @total int
select @cmd = 'select c.name, '
select @count = 1, @total = max(id) from Product
while @count <= @total
begin
select @prod = name from Product where id = @count
if(@count <> @total)
begin
select @cmd = @cmd + 'sum(CASE WHEN p.name = "' + @prod + '" THEN u.Paid ELSE 0 END) as "' + @prod + '", '
end
else
begin
select @cmd = @cmd + 'sum(CASE WHEN p.name = "' + @prod + '" THEN u.Paid ELSE 0 END) as "' + @prod + '" '
end
select @count = @count + 1
end
select @cmd = @cmd + 'from Client c ' +
+ 'inner join Purchase u on u.idClient = c.id ' +
+ 'inner join Product p on p.id = u.idProduct ' +
+ 'group by c.name'
exec(@cmd)
drop table Client
drop table Product
drop table Purchase
创建表客户端(
id int,
名称varchar(10)
)
插入到客户端值中(1,“Joe”)
插入客户端值(2,‘Marc’)
创建表格产品(
id int,
名称varchar(10)
)
插入产品价值(1,‘丰田’)
插入产品价值(2,‘福特’)
插入产品价值(3,‘菲亚特’)
创建表购买(
idClient int,
idProduct int,
支付整数
)
插入采购值(1,1,3000)
插入到购买值中(1、2、2999)
插入购买价值(2、3、4500)
插入到购买值中(2,1,1000)
声明@cmd varchar(2048)
声明@prod varchar(10),@count int,@total int
选择@cmd='选择c.name,'
从产品中选择@count=1、@total=max(id)
当@count时,您只需要使用您的表,而不是我创建的临时表来测试它!那很有用!是否有某种方法可以在不显式声明列的情况下动态创建此视图?我的意思是,假设我在DB中放入另一个产品,比如Seat,我希望相同的查询生成一个表,其中Seat包含在列中。有什么想法吗?再次非常感谢。@dariosalvi,你拿到了,如果成功,你可以投票接受答案:)
create table Client (
id int,
name varchar(10)
)
insert into Client values (1, 'Joe')
insert into Client values (2, 'Marc')
create table Product (
id int,
name varchar(10)
)
insert into Product values (1, 'Toyota')
insert into Product values (2, 'Ford')
insert into Product values (3, 'Fiat')
create table Purchase (
idClient int,
idProduct int,
Paid int
)
insert into Purchase values (1, 1, 3000)
insert into Purchase values (1, 2, 2999)
insert into Purchase values (2, 3, 4500)
insert into Purchase values (2, 1, 1000)
declare @cmd varchar(2048)
declare @prod varchar(10), @count int, @total int
select @cmd = 'select c.name, '
select @count = 1, @total = max(id) from Product
while @count <= @total
begin
select @prod = name from Product where id = @count
if(@count <> @total)
begin
select @cmd = @cmd + 'sum(CASE WHEN p.name = "' + @prod + '" THEN u.Paid ELSE 0 END) as "' + @prod + '", '
end
else
begin
select @cmd = @cmd + 'sum(CASE WHEN p.name = "' + @prod + '" THEN u.Paid ELSE 0 END) as "' + @prod + '" '
end
select @count = @count + 1
end
select @cmd = @cmd + 'from Client c ' +
+ 'inner join Purchase u on u.idClient = c.id ' +
+ 'inner join Product p on p.id = u.idProduct ' +
+ 'group by c.name'
exec(@cmd)
drop table Client
drop table Product
drop table Purchase