Search and Replace a a partial string / substring in mssql tables

Question

I was tasked with moving an installation of Orchard CMS to a different server and domain. All the content (page content, menu structure, links, etc.) is stored in an MSSQL database. The good part: When moving the physical files of the Orchard installation to the new server, the database will stay the same, no need to migrate it. The bad thing: There are lots and lots of absolute URLs scattered all over the pages and menus.

I have isolated / pinned down the tables and fields in which the URLs occur, but I lack the (MS)SQL experience/knowledge to do a "search - replace". So I come here for help (I have tried exporting the tables to .sql files, doing a search-replace in a text editor, and then re-importing the .sql files to the database, but ran into several syntax errors... so i need to do this the "SQL way").

To give an example:

The table Common_BodyPartRecord has the field Text of type ntext that contains HTML content. I need to find every occurance of the partial string /oldserver.com/foo/ and replace it with /newserver.org/bar/ . There can be multiple occurances of the pattern within the same table entry.

(In total I have 5 patterns that will need replacing, all partial string / substrings of urls, domains/paths, etc.)

I usually do frontend stuff and came to this assignment by chance. I have used MySQL back in the day I was playing around with PHP related stuff, but never got past eh basics of SQL - it would be helpful if you could keep your explainations more or less newbie-friendly.

The SQL server version is SQL Server 9.0.4053 , I have access to the database via the Microsoft SQL Server Management Studio 12

Any help is highly appreciated!

Answer 1

You can't manipulate the NTEXT datatype directly, but you can CAST it to VARCHAR(MAX) , then use the REPLACE function to perform the string replacement, then CAST it back to NTEXT. This can all be done in a single UPDATE statement.

update MyTable 
    set MyColmun = cast(replace(cast(MyColumn as nvarchar(max)), N'/oldserver.com/foo/', N'/newserver.org/bar/') as ntext)
    where cast(MyColumn as nvarchar(max)) LIKE N'%/oldserver.com/foo/%'

The WHERE clause in the UPDATE statement below is used to prevent SQL Server from making non-changes, ie if the value does not need to be changed then there is no need to update it to itself.

The CAST function is used to change the data type of a value. NTEXT is a legacy data type used for storing large character values, NVARCHAR(MAX) is a new and more versatile data type for storing large character values. The REPLACE function can not operate on NTEXT values, hence the need to CAST it to NVARCHAR(MAX) first, do the replace, then CAST it back to NTEXT afterwards.