Union Question

I have a union that goes something like this:

select A, B from table1
union all
select X, Y from table2

but in my case, I need to cast col Y to a null in the second select, so
the union turns into

select A, B from table1
union all
select X, cast(null as varchar(10)) from table2

The VarChar(10) is the size of col B.  Hardcoding the size of the
varchar in this situation seem awkward, but appears to be necessary.
What I tried (but it didnt work) is using a domain instead of the
varchar cast.

* Doesnt work
select A, B from table1
union all
select X, cast(null as MyDomainType) from table2

My concern is that during maintenance updates, the column size could
change which could inadvertantly affect the union. This column size
dependence isn't readily apparent.  Specially for new folks that may be
maintaining the database.

Is there any other way to make this kind of SQL more generic so the
casting is based on the actual column type so that you could make a
size change in one place?




-- 

> Is there any other way to make this kind of SQL more generic so the
> casting is based on the actual column type so that you could make a
> size change in one place?

Not currently, no.


-- 
Martijn Tonies
Database Workbench - tool for InterBase, Firebird, MySQL, NexusDB, Oracle &
MS SQL Server
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