SQL Server Compact Query Analyzer: How to change part of a string value in a table? - sql

Question

I have an SQL Server Compact Edition 4.0 database file which has .sdf extension. The database is created by a book cataloging application. The database has many tables, among them a table called Book which contains one row for each book in the database. The table has many columns among them a column called FrontCover which contains a string value which has 2 parts: path part and file name part of the image file for the front cover of a book, for example:
Documents and Settings\Boson\My Documents\Books\Covers\0596003978.jpg
In this example path part is:
'Documents and Settings\Boson\My Documents\Books\Covers'
while file part is:
'0596003978.jpg'
Some books do not contain any value for the column FrontCover because the front cover is not available. For such books column FrontCover is empty. However if a book has a front cover image file then the string value has the same path part but different file part. For example for another book column FrontCover has this value:
'Documents and Settings\Boson\My Documents\Books\Covers\1590596633.jpg'
As we can see the path part is the same as in the first example, namely:
'Documents and Settings\Boson\My Documents\Books\Covers'
but the file part is different:
'1590596633.jpg'
PROBLEM:
I want to change the whole table Book so that string values of the column FrontCover are modified for every book in the table in such a way that file part is kept the same but the path part is changed from:
'Documents and Settings\Boson\My Documents\Books\Covers'
to
'Books\AEM database\Covers'
The string value of the column FrontCover for the book in the first example would thus change from:
'Documents and Settings\Boson\My Documents\Books\Covers\0596003978.jpg'
to
'Books\AEM database\Covers\0596003978.jpg'
File part is the same but the path part is changed. I want to change the whole Book table so that the file part of the string value for column FrontCover is kept the same but the path part is changed as specified above.
The book cataloging application which owns the .sdf database file is stupid and cannot do the job. Therefore I have installed a simple open source SQL viewing/editing application called SQL Compact Query Analyzer (http://sqlcequery.codeplex.com/). SQL Compact Query Analyzer can open .sdf database files and accepts SQL commands in order to modify the .sdf database file.
Can you please help me with the SQL commands which can do the job?
Thank you very much in advance for your help.
best regards

Answer 1

UPDATE Book SET FrontCover = REPLACE(
CAST(FrontCover AS NVARCHAR(300)),
'Documents and Settings\Boson\My Documents\Books\Covers',
'Books\AEM database\Covers')
WHERE FrontCover like
'Documents and Settings%'
Note: the where clause may not be necessary but it ensures that you only replace strings that start with 'Documents and Settings...'

Answer 2

The answer posted by Paul Brown is OK however it produced the following error code:
ErrorCode: -2147467259 [SQL Server Compact ADO.NET Data Provider] HResult: -2147217900, NativeError: 25922 ErrorMessage: The specified argument value for the function is not valid. [ Argument # = 1,Name of function(if known) = REPLACE ]
The reason for this is because the type of date for the column FrontCover is NTEXT (I forgot to specify that in my question) and function REPLACE does not allow NTEXT variable. So we have to covert FrontCover variable with the following command before passing it to REPLACE:
CAST(FrontCover AS NVARCHAR(100))
Therefore the answer to my question is:
UPDATE Book
SET FrontCover = REPLACE (CAST(FrontCover AS NVARCHAR(100)), 'Documents and Settings\Boson\My Documents\Books\Covers\', 'Books\AEM database\Covers\')