How should I update ID field values for all records based on previous values?

Question

I need a SQL query that can update ID fields for all records in a table from their previous values to a new value based on that previous value.

For example, if the ID is 1, I want to change it to 9991 - prepending '999' to every ID in the table.

What is the most efficient means of doing this?

Answer 1

A couple options come to mind. If you have a charish data type:

update table set column=concat('999',column);

If you have an integer type find the max value, let's say it's under 10,000 then

update table set column=9990000+column