Question

I have a large table of data with a new field added called uniq_id what I am looking for is a query I can run that will update and increment this field for each row, without having to write a script to do this.

Any ideas?

Answer 1

What other columns does the table have? If you define the new column with AUTO_INCREMENT MySQL will fill it with sequential values starting from 1. There’s a catch though: the column has to be a key, or at least a part of the key (see the documentation for details). If you don’t have a primary key in the table already, you can simply do this:

alter table MyTable add uniq_id int auto_increment, add primary key (uniq_id);

If you can’t change the keys in the table and just want to fill the values of the new column as a one-off thing, you can use this update statement:

update MyTable set uniq_id = (@count := coalesce(@count+1, 1));

(coalesce returns its first non-null argument; it effectively establishes the value of the column for the first row.)