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Script to change nvarchar to varchar for all my tables

Posted on 2009-05-14
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I need some T-SQL script to change all "nvarchar" columns to "varchar" for all my tables in my database.  How would I do this?
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Question by:schmir1
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Richard Quadling earned 100 total points
ID: 24389374
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by:BrandonGalderisi
ID: 24389422
I assume you are positive that your columns have no unicode data?
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by:schmir1
ID: 24389683
Thanks.  I'm trying to run your script in the Server Management Studio but get the following errors:

Msg 5074, Level 16, State 1, Line 1
The object 'UK_principal_name' is dependent on column 'name'.
Msg 4922, Level 16, State 9, Line 1
ALTER TABLE ALTER COLUMN name failed because one or more objects access this column.
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by:Anthony Perkins
ID: 24391650
You are going to have to do this manually.
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by:BrandonGalderisi
ID: 24391718
Or do a major overhaul on the procedure so that it drops and re-creates the dependent objects.
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by:csenasa
csenasa earned 100 total points
ID: 24392641
Hi,

Try this. It will Change the Nvarchar Columns to Varchar of all tables at one shot!!

NOTE : IF there are Any Key Constraints present on the Column then those columns will fail.
DECLARE @VarQuery VARCHAR(8000)
SELECT  @VarQuery = ISNULL(@VarQuery + ';' , '' ) +  'ALTER TABLE ' + TAble_Name + ' ALTER COLUMN ' 
+   Column_Name + ' VARCHAR(' +  CAST(Character_MAximum_length as VARCHAR(12)) + ') ; '--, * 
FROM Information_schema.columns where Data_type = 'nvarchar'
 
SELECT (@VarQuery)

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by:BrandonGalderisi
BrandonGalderisi earned 200 total points
ID: 24396541
cesnasa: your script suffers from the same thing that the first posted answer does in that it does not account for dependant objects.  it is already evident that there ARE dependent objects based upon the supplied error.
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by:schmir1
ID: 24397280
cesnasa:  I tried it with a test table but it didn't change anything even though this test table didn't have any constraints?  I get the following in the results window.

I'm starting to be convince that I will have to do it manually.  So far my SQL Server experiences are that it is very hard to do anything)-:
ALTER COLUMN Test Format VARCHAR(20) ; ;ALTER TABLE test ALTER COLUMN col1 VARCHAR(50) ; ;ALTER TABLE test ALTER COLUMN col2 VARCHAR(50) ;

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by:BrandonGalderisi
ID: 24397676
Another problem with csenasa's post is that it doesn't take into account the current NULL setting of a column.  You could potentially be changing all of your columns to the default of NULL.
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by:Anthony Perkins
Anthony Perkins earned 100 total points
ID: 24398155
>>I'm starting to be convince that I will have to do it manually<<
I agree.
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by:BrandonGalderisi
BrandonGalderisi earned 200 total points
ID: 24398438
"I'm starting to be convince that I will have to do it manually"

Manually or through SSMS where it handles a lot of this stuff for you.

JUST KNOW!!!!! that indexes are bound to those columns as well.  And if you are changing the data type of a column, any and all indexes that depend on that table will be rebuilt.  If you have any large tables, that could be time consuming.  

Perhaps you would be best served attempting this in a test environment first.
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Author Comment

by:schmir1
ID: 24484319
It took about 3 hours but I did it manually.  Thanks for all your suggestions.
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