deltaHelper Documentation Series -- DELTA_TableExists

mike.brockey — Thu, 26 Oct 2006 06:02:00 GMT

I will start the series with the DELTA_TableExists function that is provided in the deltaHelper script. We have implemented certain guidelines on our team for writing deltas. One guideline required that all delta be repeatable. As you may have already noticed, deltaRunner enforces this policy by executing deltas in development mode two times. Writing deltas in this way force us to think about the database prior to just making changes. We use this function in our delta files to ensure that we are only adding a table to the database once. To make changes to a table, we will use a procedure called DELTA_ColumnAdder or one of a few other variants. More on this in a later post.

The DELTA_TableExists function provides an easy way to determine if a table already exists in the database. Lets say for any number of reasons you wanted to know if a table exists in your database. In this example we will do some work if we know a specified table already exists in the database.

if(dbo.DELTA_TableExists('TABLENAME') = 1)
begin
-- TABLE EXISTS ... DO SOME WORK
end
go

Or you might want to check to see the table does not exists.

if(dbo.DELTA_TableExists('TABLENAME') = 0)
begin
-- TABLE DOES NOT EXIST ... DO SOME WORK
end
go

deltaHelpers added to the EntropyZero TDD Developer's Toolkit

mike.brockey — Sat, 21 Oct 2006 17:07:00 GMT

How many times do you have to write a query against the information_schema.tables view before you finally remember the name of it and where that underscore goes?

deltaHelpers are a collection of stored procedures and sql functions that are a direct result of database refactoring. Prior to these functions the code was sprinkled all over my deltas and are now in a single place to remove duplication. With functions like DELTA_ColumnAdder and DELTA_TableExists, these deltaHelpers allow you to write better functioning deltas with fewer lines of code.

I will document the usage of each of these functions in the coming days/weeks in future blog posts. Most of the deltas are pretty well documented and have sample usages and remarks in the downloadable sql script.

Mike_Brockey[0].Blog() : deltaHelpers, EntropyZero

deltaHelper Documentation Series -- DELTA_TableExists

deltaHelpers added to the EntropyZero TDD Developer's Toolkit