How to create a mysql add column if it does not exist?

To create a mysql add column if not exists

  MySQL ALTER TABLE does not have IF EXISTS specification.

You can do the following through using a stored proc or a programming language if this is something that you'll need to do on a regular basis:

Pseudocode:

Find if the column exists using the SQL below:
SELECT column_name FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA=[Database Name] AND TABLE_NAME=[Table Name];

If the above query returns a result then it means the column exists, otherwise you can go ahead and create the column.