SqlDataSource中的SQL Join查询

Question

I am not really sure about how to do this.

In a table Product1 I have:

Id, Code, Description, Group, Quantity, Unit, Cost, Note

In the other table Componets I have:

Id, Code, Description, Unit, Cost, Note

The problem I am facing is that while table Components has always all columns with data, table Product1 should take the data relevant "Description, Unit and Cost" from table "Components". In this table "Product1" basically only the Code, Quantity, Group and Note are added by the user.

Is this possible to achieve this with a query made in a SqlDataSource ? I have no idea on how to do this and I would appreciate your help.

So far this is what I tried:

SELECT 
   Product1.Code, Group, Quantity, Product1.Note
FROM
   dbo.Product1
INNER JOIN 
   dbo.Components ON Components.Code = Product1.Code

But I do not get what I need, I get only Code , Group , Quantity and Note from Product1 table

Answer 1

It means your fields (columns) Code and Note appear in both tables; thus one should use a table prefix, which points out from which table one will fetch the column:

SELECT Components.Code AS 'Components Code', Product1.Code AS 'Product Code', Groupp, Quantity, Components.Note AS 'Components Node', Product1.Note AS 'Product Note'

FROM
dbo.Product1

INNER JOIN dbo.Components
ON Components.Code = Product1.Code

As demonstrated above, one can include multiple columns and give them a label when fetched.

Answer 2

First, lets understand why they are 'ambiguous'.

Because your join is on two tables both having the same column names. Since, you have not specified the table name for those columns, the SQL engine is confused which table you want those columns from? Hence, it says ambiguous. Just use an alias as such:

GENERAL IDEA :

SELECT tab.id, tab.Name

FROM TableName tab

WHERE tab is called the alias.

With respect to you question, this the query you need:

SELECT         prod.Code,
               prod.Groupp,
               prod.Quantity,
               prod.Note,
               comp.Description,
               comp.Unit,
               comp.Cost

FROM           dbo.Product1 prod    
INNER JOIN     dbo.Components comp
ON             comp.Code = prod.Code
//Any Where conditions should follow here

Observe how prod and comp are used as the aliases. They will not cause you any 'ambiguity'.

Hope this helps!!!