How to store NULL values in datetime fields in MySQL?

Question

I have a \"bill_date\" field that I want to be blank (NULL) until it\'s been billed, at which point the date will be entered.

I see that MySQL does not like NULL val

Answer 1

Specifically relating to the error you're getting, you can't do something like this in PHP for a nullable field in MySQL:

$sql = 'INSERT INTO table (col1, col2) VALUES(' . $col1 . ', ' . null . ')';

Because null in PHP will equate to an empty string which is not the same as a NULL value in MysQL. Instead you want to do this:

$sql = 'INSERT INTO table (col1, col2) VALUES(' . $col1 . ', ' . (is_null($col2) ? 'NULL' : $col2). ')';

Of course you don't have to use is_null but I figure that it demonstrates the point a little better. Probably safer to use empty() or something like that. And if $col2 happens to be a string which you would enclose in double quotes in the query, don't forget not to include those around the 'NULL' string, otherwise it wont work.

Hope that helps!