从一个表中获取一列，而从另一表中获取两列

Question

I'm trying to combine the results in one output where one column is DepositNo and the other is Doc_Type where any Doc_Type equals to DocType (vise versa), the DepositNo of DocType is displayed.

Here's my query:

SELECT Doc_Type
  FROM Doc_Outgoing_Details
 WHERE (Doc_Type <> 67)
UNION
SELECT DepositNo, DocType AS Doc_Type
  FROM Doc_Outgoing
 WHERE (DocType <> 67)

When I execute it, it says:

UNION must have and equal number of expressions in their target list.

Answer 1

when You use union you should match all columns and your result sets should have same numbers of columns so you need to generate Doc_Type column in your fist query too :

SELECT        Doc_Type,0 as Doc_Type  // or every value 
                                      //that you didn't use in real DOCTYPE
FROM            Doc_Outgoing_Details
WHERE        (Doc_Type <> 67)
UNION
SELECT        DepositNo, DocType AS Doc_Type
FROM            Doc_Outgoing
WHERE        (DocType <> 67)

Answer 2

Because the number of columns projected on your SELECT statement doesn't match. The first one contains one column and other second one has two. Try adding null value on the first query,

SELECT    Doc_Type as DepositNo, NULL Doc_Type
FROM      Doc_Outgoing_Details
WHERE     Doc_Type <> 67
UNION
SELECT    DepositNo, DocType AS Doc_Type
FROM      Doc_Outgoing
WHERE     DocType <> 67

Answer 3

What you are looking for is INNER JOIN .

SELECT d.DepositNo, D.Doctype
FROM Doc_Outgoing d
INNER JOIN Doc_Outgoing_Details do
    ON d.Doctype = do.Doc_type
WHERE (d.DocType <> 67)

Answer 4

you are missing a column on your second table . UNION must have equal number of columns . This should work.

SELECT        O AS DepoSitNo, Doc_Type
FROM            Doc_Outgoing_Details
WHERE        (Doc_Type <> 67)
UNION
SELECT        DepositNo, DocType AS Doc_Type
FROM            Doc_Outgoing
WHERE        (DocType <> 67)