Sql-server – Generate script to automate renaming of default constraints

dynamic-sqlsql serversql-server-2008-r2

Background: Some of our default column constraints were generated without explicit names, so we get fun names that vary from server to server like: DF__User__TimeZoneIn__5C4D869D

I would prefer to have them all manageable with a consistent naming like DF_Users_TimeZoneInfo so that we can ensure that the appropriate constraints exist on future target tables (like in RedGate compare, or even just visually)

I've got a script that mostly works for what I want:

select 'sp_rename N''[' + s.name + '].[' + d.name + ']'', 
   N''[DF_' + t.name + '_' + c.name + ']'', ''OBJECT'';'
from sys.tables t
    join
    sys.default_constraints d
        on d.parent_object_id = t.object_id
    join
    sys.columns c
        on c.object_id = t.object_id
        and c.column_id = d.parent_column_id
    join sys.schemas s
        on t.schema_id = s.schema_id
WHERE d.NAME like 'DF[_][_]%'

But this just gives me a resultset, and not something I can actually pass into an exec or whatever.

How can I make this so I can just execute those sp_rename scripts without having to resort to copying out all the returned elements and pasting them into a new query window and running them again? Trying to save as many keystrokes as possible so I can correct this in many environments.

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Best Answer

Ok, couple of things.

  1. always use EXEC when executing stored procedures; the shorthand without EXEC only works when it is the first statement in the batch (and that will not be the case here).
  2. always use semi-colon terminators - in this case they are useful in lieu of pretty carriage returns and indentation, but they are always wise to have.
  3. always use QUOTENAME() instead of manually applying square brackets yourself. In this case you're probably safe, but there are cases where the manual approach will break.

  4. you can test the PRINT output but it won't necessarily be complete if your total command is > 8k (see this tip for some alternative approaches).

    DECLARE @sql nvarchar(max) = N'';

SELECT @sql += N'EXEC sys.sp_rename N''' 
    + QUOTENAME(s.name) + '.' + QUOTENAME(d.name) 
    + ''', N''DF_' + t.name + '_' + c.name + ''', ''OBJECT'';'
  FROM sys.tables AS t
  INNER JOIN sys.default_constraints AS d
     ON d.parent_object_id = t.object_id
  INNER JOIN sys.columns AS c
     ON c.object_id = t.object_id
    AND c.column_id = d.parent_column_id
  INNER JOIN sys.schemas AS s
     ON t.schema_id = s.schema_id
  WHERE d.NAME LIKE N'DF[_][_]%';

PRINT @sql;
-- EXEC sys.sp_executesql @sql;
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