This is just a quick tip and reminder as of how to change a column in a MySQL table from NULL to NOT NULL. Changing a column is done by using ALTER TABLE together with MODIFY, a working example is included below:
ALTER TABLE mytable MODIFY mycolumn BIGINT(20) NOT NULL;
Changing from NULL to NOT NULL from PHP
The above command can be entered in a terminal after logging in on your MySQL server. Alternatively, you can also send the query from PHP, in which case you would likely want to do something like below:
$this->query("ALTER TABLE mytable MODIFY mycolumn BIGINT NOT NULL");
The above PHP code is object oriented, if you are getting errors, or do not know what the "$this->" part is, then you likely don't need it.