MYSQL: How to make NULL or empty data default to 0 during insert

Question

So this seems like it would be pretty straight forward and I swear I\'ve done this before, but for some reason it\'s just not working for me.

I am using MAMP

Answer 1

You forgot to post the INSERT queries but I'm sure the problem is there. This works as expected:

insert into listings (ListingID) values(1)

... because you omit BathsFull so MySQL uses the defalt. This doesn't:

insert into listings (ListingID, BathsFull) values(1, null);

... because your are telling MySQL that you want NULL.

Answer 2

You can use the default keyword to get the default value of the column during insertion.

Example :

INSERT INTO listings(ListingID, BathsFull) VALUES (2,DEFAULT);

Answer 3

If you are explicitly setting the value to NULL in your insert, but want MySQL to replace the NULL with 0, one way to do that is to define the column to allow NULL in the CREATE TABLE statement, and then replace the NULL with a TRIGGER.

Something like this:

CREATE TABLE `listings` (
  `ListingID` int(11) NOT NULL,
  `BathsFull` int(6) NULL DEFAULT 0,
  PRIMARY KEY (`ListingID`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

delimiter $$

create trigger tr_b_ins_listings before insert on listings for each row
begin
  set new.BathsFull = coalesce(new.BathsFull,0);
end $$

delimiter ;

Try it for yourself in this SQL Fiddle

Answer 4

Maybe you should try this:

insert into listings (ListingID, ListingID, BathsFull) 
values (@listing_id, @ListingID, isnull(BathsFull, 0)

Answer 5

You can definitely use a trigger for that

Assuming that you make the field nullable

CREATE TABLE `listings` (
  `ListingID` int(11) NOT NULL,
  `BathsFull` int(6),              <-----
  PRIMARY KEY (`ListingID`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

Trigger

DELIMITER $$
CREATE TRIGGER tg_lst_insert BEFORE INSERT ON listings
FOR EACH ROW
BEGIN
    SET NEW.BathsFull = IFNULL(NEW.BathsFull, 0);
END $$
DELIMITER ; 

Inserting some rows

INSERT INTO `listings` VALUES(1, '');
INSERT INTO `listings` VALUES(3, 'a');
INSERT INTO `listings` VALUES(4, NULL);
INSERT INTO `listings` (ListingID) VALUES(2);
INSERT INTO `listings` VALUES(5, 3);

Result

+-----------+-----------+
| ListingID | BathsFull |
+-----------+-----------+
|         1 |         0 |
|         2 |         0 |
|         3 |         0 |
|         4 |         0 |
|         5 |         3 |
+-----------+-----------+