Table of Types Examples

Posted on 2014-03-18
Medium Priority
Last Modified: 2014-03-21
I've got dozens of "type" tables that are mostly identical and I would like to consolidate them all into a handful of tables. (i.e. a table of types)

For example, the tables Permit Type, Employee Type, Line Type, Vendor Type, etc.  all have the same basic columns:

There are a few that might have an additional attribute column, but for the most part they're just an ID and a Name.

Does anyone have a link to an example of creating a table of types, or just advice in general?
Question by:Torrwin
LVL 35

Assisted Solution

by:Paul MacDonald
Paul MacDonald earned 1000 total points
ID: 39937447
Just because they're all structured similarly, doesn't mean you should consolidate them.  It also doesn't mean you shouldn't.  What matters is how you query them.

That said, you could create a new table, identical in structure to what you already have, but with a couple additional columns indicating what the record is a type of (and an index for the new, consolidated table), so something like...

MetaType <- something indicating Permit, Employee, Line, Vendor, etc.

Bear in mind, this will necessitate rewriting ALL the queries that use these tables.
LVL 70

Accepted Solution

Scott Pletcher earned 1000 total points
ID: 39938248
It's usually best to use a numeric code for the "metatype" / lookup_table_code for performance reasons.  Another table can contain the descriptive name of the underlying table.

For example, table "Permit Type" might be 1, "Employee Type" might be 2, etc..

Often a smallint allows enough values, you don't typically have to use a full int.

The combined table should be clustered on ( lookup_table_code, <lookup_value> [X_Type_Id] ).

That is, queries would still join to, say, table [Permit Type], but now it's a view, like this:
CREATE VIEW [Permit Type]
FROM dbo.lookup_table
    lookup_table_code = 3 --<or> "= (SELECT lookup_table_code FROM lookup_table_directory WHERE name = 'Permit Type')"

>> Bear in mind, this will necessitate rewriting ALL the queries that use these tables. <<

Not necessarily.  You could instead create views with the same names as the existing tables.  Indeed, I'd strongly suggest using the combined lookup table that way anyway, rather than having each query specify the lookup table code.

Of course, once the view is created, it replaces the original table name completely, so the name then only points to the new table.

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