Sql insert ignore does not work because of timestamp now()

Question

I am trying to prevent duplicate entries like this

INSERT IGNORE INTO myTable( `val_1`, `val_2`, `val_3`, `date` ) 
VALUES ( '$var_1', '$var_2', '$var_3', now() )

The values i would like to check are the 3 val_x but because now() will be a unique value, insert ignore does not work.

How can i not check that last variable as unique?

note: this is kind of like a cart, so i cannot make the first 3 values unique. There is a session variable that allows each user to see aa unique collection.

From this diagram, the first 2 rows are duplicate since they belong to the same user session. The 3rd row is not a duplicate becase it belongs to a different user session

 +---------+-------+--------+
 | session | var 1 | var 2  |
 +---------+-------+--------+
 | abc1234 | aaaaa | bbbbb  |
 +---------+-------+--------+
 | abc1234 | aaaaa | bbbbb  |
 +---------+-------+--------+
 | 5678def | aaaaa | bbbbb  |
 +---------+-------+--------+
 | 5678def | aaaaa | ccccc  |
 +---------+-------+--------+

as paqogomez suggested i removed now() from the query and altered the table but it looks like i need a primary key for insert ignore to work, but for my scenario i cant make these 3 columns unique

ERROR 1062: Duplicate entry 'aaaaa' for key 'var 1'

Answer 1

Create a unique index on the first three columns:

create unique index myTable_session_val2_val3 on myTable(session, val_1, val_2);

This will guarantee that combinations of these three are unique, without taking into account any other columns.

Answer 2

I would suggest moving the date into the default value of the column.

ALTER TABLE mytable CHANGE `date` `date` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP

This way, you can still deal with the duplicates in the data in PHP. The alternative, as others have suggested would result in a database foreign key error if you attempted to insert a duplicate.

Then this sql would work and give the same result:

INSERT IGNORE INTO myTable( `val_1`, `val_2`, `val_3` ) 
VALUES ( '$var_1', '$var_2', '$var_3' )

EDIT:

You still need a unique index to make it work. See @Gordon's answer

Answer 3

You should probably define the UNIQUE keys for the combination of columns you don't want to be duplicated. So, don't specify column date as UNIQUE . Did you verify that? Define rest of three values as unique columns. It will probably work.