Question

I have a MySQL table with 4 columns

Column  Type        Null  Default
----------------------------------
id      int(11)     No    None     AUTO_INCREMENT
col1    int(11)     No    None
col2    int(11)     No    None
col3    varchar(20) Yes   Null

I have created a index with col1, col2, col3 since I don’t want duplicate rows. I understand that NULL value is considered distinct so the table accepts duplicate rows.

What is the best alternative so I can have rows with unique values for col1, col2, col3?

Answer 1

You could set NOT NULL on col3 and set the default value to ''.