MySQL PHPMyAdmin Error #1062 - Duplicate entry '0' for key 'PRIMARY'
Now I want to add a primary key id column but it throws the error:
#1062 - Duplicate entry '0' for key 'PRIMARY'
I already tried this: Add primary key to existing table
Answer
When you creates a new column, a default value is asigned (in your case will be 0), so you need to specify wich values will it have (besides you can tell it to the column to be autoincremental, and it will do the work for you for the new entries of rows). You have to change all the values to be differents between them, the id key MUST be unique
To change all your ids, in mysql you can do:
SET @new_id=0;
UPDATE your_table
SET id = @new_id := @new_id + 1
where id = 0