Generating change scripts in SQL Server 2005 Management Studio
In the typical dev environment, there is a development server, a functional testing server, a quality assurance server, and one or more production servers. Let's suppose that your mandate is to modify a table on the development server, adding a column or changing a column's name or data type, and yet you still have 50 or so more changes to make. Now it's time to roll out the changes to the other servers in cascading order.
SQL Server 2005 Management Studio comes to the rescue with its handy Generate Change Script button, which you can see in Figure A. The Generate Change Script button appears after you right-click a table and choose Modify from the shortcut menu. The code attached to the button analyzes the current table definition, compares it to your changed definition, and writes a script that will alter the old table to conform to the new definition. By running this script on a remote database, you can make changes to databases installed at client or branch sites.
| Figure A |
Figure A: Generate Change Script button |
Now you're asked to change all nchar and nvarchar columns to char and varchar respectively. This could be a minefield, particularly where foreign keys are concerned. (For the moment, we will sidestep the issue of using such columns as primary keys, as opposed to identity columns.)
When you begin to make these changes, you'll discover another cool hidden feature in SQL Server 2005 Management Studio: the Data Type Change. The dialog box will appear if you change the data type or anything else on a column that is a foreign key. For example, after changing all instances of nchar to char and nvarchar to varchar, the Data Type Change Required dialog box (see Figure B) popped up. After reading the warning that I might lose data due to the conversion, I clicked the Yes button to proceed.
| Figure B |
Figure B: SQL Server 2005 Management Studio detects that the CustomerID column is a foreign key elsewhere, and notifies you that all instances will be changed. |
SQL Server 2005 Management Studio generated the code to perform all these changes and presented me with a preview for my verification. (Note: In the preview window, you can't see all the code, but you can select it all and paste it into an editor for easier viewing.) Listing C contains the generated code.
If you are faced with this type of change request and it reverberates through your entire database, then generating individual scripts like the one presented above can be quite tedious. You can save time by using various solutions, such as data-modeling tools or Red Gate Software's SQL Compare, which can "diff" two databases and update one from the changes made to the other. But, when your tasks are less monumental, SQL Server 2005 Management Studio does a wonderful job.
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