SQL Server Management Studio - How to Change a Field Type Without Dropping Table

SQL Server Management Studio - how to change a field type without dropping table

Just use T-SQL script instead of the visual designer to achieve your goal:

ALTER TABLE dbo.YourTableNameHere
ALTER COLUMN YourColumnNameHere DECIMAL(18, 14) 

and you should be fine.

The visual designer takes the extra careful route of creating the table with the new structure and then copying over all the data - it works, but it's tedious. Normally, as long as you don't truncate a column (make it shorter), you can definitely change the column's datatype "in place" using a T-SQL statement.

Also: by default the SSMS designer is extra careful and won't allow any changes that require a drop-and-recreate table cycle. You can disable this extra carefullness in Tools > Options and then in this dialog box:

If you uncheck that option, you will be able to do "destructive" changes in your visual designer

How to change a column without dropping a table in SQL 2008

In SQL Server 2008, go to Tools >> Options. In the little window, click "Designer". Uncheck "Prevent saving changes that require ..."

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Edited on Sept 4th, 2015.

I have added this answer here a long, long time ago describing the way I would solve the situation described on the question above. Since then, users on the threads below have exposed several concerns on doing things the way I recommended at the time. Basically, the solution I described could be problematic on some scenarios. I then suggest you to keep on reading to check other users' comments and pick the best solution for you.

Changing the data type without dropping the table in sql server 2008

See this answer:
SQL Server Management Studio - how to change a field type without dropping table

The visual designer takes the extra careful route of creating the table with the new structure and then copying over all the data - it works, but it's tedious. Normally, as long as you don't truncate a column (make it shorter), you can definitely change the column's datatype "in place" using a T-SQL statement.

Also: by default the SSMS designer is extra careful and won't allow any changes that require a drop-and-recreate table cycle. You can disable this extra carefullness in Tools > Options and then in this dialog box:

If you uncheck that option, you will be able to do "destructive" changes in your visual designer

How to change column datatype in SQL Server database without losing data?

You can easily do this using the following command. Any value of 0 will be turned into a 0 (BIT = false), anything else will be turned into 1 (BIT = true).

ALTER TABLE dbo.YourTable
   ALTER COLUMN YourColumnName BIT

The other option would be to create a new column of type BIT, fill it from the old column, and once you're done, drop the old column and rename the new one to the old name. That way, if something during the conversion goes wrong, you can always go back since you still have all the data..

How to change the data type of a column without dropping the column with query?

If ALTER COLUMN doesn't work.

It is not unusual for alter column to fail because it cannot make the transformation you desire. In this case, the solution is to create a dummy table TableName_tmp, copy the data over with your specialized transformation in the bulk Insert command, drop the original table, and rename the tmp table to the original table's name. You'll have to drop and recreate the Foreign key constraints and, for performance, you'll probably want to create keys after filling the tmp table.

Sound like a lot of work? Actually, it isn't.

If you are using SQL Server, you can make the SQL Server Management Studio do the work for you!

• Bring up your table structure (right-click on the table column and select "Modify")
• Make all of your changes (if the column transformation is illegal, just add your new column - you'll patch it up in a moment).
• Right-click on the background of the Modify window and select "Generate Change Script." In the window that appears, you can copy the change script to the clipboard.
• Cancel the Modify (you'll want to test your script, after all) and then paste the script into a new query window.
• Modify as necessary (e.g. add your transformation while removing the field from the tmp table declaration) and you now have the script necessary to make your transformation.

Change column type without losing data

You don't need to add a new column two times, just remove the old one after updating the new one:

ALTER TABLE table_name ADD new_column_name decimal(18,2)

update table_name
set new_column_name = convert(decimal(18,2), old_column_name)

ALTER TABLE table_name DROP COLUMN old_column_name

Note that if the old_column_name is not numeric, the convert may fail.

How to change datatype whithout dropping dependencies

We found a way to do this. Although it probably isn't the best solution, it worked for us so if anyone has the same problem, try the following:

In SQL Server Management Studio go to Tools -> Options -> Designer and uncheck the box of "Prevent saving changes that require table re-creation"

Next rightclick the table you want to modify the column datatypes and click on "Design".

In the designer, edit the column datatype to the one you need.

Finally, right-click and choose "Generate Change Script".

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What it does is the following:

• Drop the constraints on the table
• Create a temp table with the new datatype of the column
• Readd constraints to the temp table
• Set the IDENTITY_INSERT on the temp table to ON
• Copy all data from the old table to the new temp table
• Set the IDENTITY_INSERT on the temp table to OFF
• Drop the old table
• Rename the temp table to the name of the old table
• Readd the primary key constraint
• Recreate the indexes
• Readd the foreign key constraints

Additionally you have to refresh all depending views.
You can generate the statements with this script:

SELECT DISTINCT 'EXEC sp_refreshview ''' + s.name + '.' + so.name + '''' AS 'dbo.TABLENAME'
FROM sys.objects AS so 
INNER JOIN sys.sql_expression_dependencies AS sed 
    ON so.object_id = sed.referencing_id 
INNER JOIN sys.schemas AS s
    ON so.schema_id = s.schema_id
WHERE so.type = 'V' AND sed.referenced_id = OBJECT_ID('dbo.TABLENAME');

• Check the box of "Prevent saving changes that require table re-creation" in Tools -> Options -> Designer

Please be careful about this! See if it really does what you are looking for. Keep in mind that this drops the old table. Test this in a development environment!

Saving changes after table edit in SQL Server Management Studio

Go into Tools -> Options -> Designers-> Uncheck "Prevent saving changes that require table re-creation". Voila.

That happens because sometimes it is necessary to drop and recreate a table in order to change something. This can take a while, since all data must be copied to a temp table and then re-inserted in the new table. Since SQL Server by default doesn't trust you, you need to say "OK, I know what I'm doing, now let me do my work."

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