Update SQL with consecutive numbering within a group

Question

I found the technique to update rows of a table with consecutive numbers here:

Update SQL with consecutive numbering

The gist of the technique is to use (T-SQL):

update myTable
SET @myvar = myField = @myVar + 1

which is awesome and works very well.

Can this technique be extended to number different groups of records, with each group starting with 1 ? eg

• Category 1 rows should get a sequence number 1,2,3,....
• Category 2 rows should also get a sequence number 1,2,3,.....

Answer 1

You can simply add a WHERE Clause to your UPDATE statement. see http://dev.mysql.com/doc/refman/5.0/en/update.html for reference.

Basically you do something like:

update myTable
SET @myvar = myField = @myVar + 1
WHERE myCategory = 'CAT'