Add support for IS NOT NULL

[yesdevnull]

Allows for correct 'value' != null comparisons in SQL.

I've tested this with MSSQL but the syntax for MySQL looks to be the same.

[Naktibalda]

Please add tests for IS NULL and IS NOT NULL to https://github.com/Codeception/module-db/blob/master/tests/unit/Codeception/Lib/Driver/DbTest.php

[yesdevnull]

Requested changes and tests done, back to you @Naktibalda.

[Naktibalda]

Thanks.

Would it be too much to ask you to document operators in Query Generation section?
https://github.com/Codeception/module-db/blob/master/src/Codeception/Module/Db.php#L198-L231

[yesdevnull]

@Naktibalda documentation added. Let me know if you want it fleshed out further (or if you would like me to document the other operators.)

[Naktibalda]

Thanks.

I looked at documentation page again and found that Supported operators are documented under seeInDatabase, dontSeeInDatabase and grabFromDatabase, but not under seeNumRecords and grabNumRecords.

Comparison expressions can be used as well:

<?php
$post = $I->grabFromDatabase('posts', ['num_comments >=' => 100]);
$user = $I->grabFromDatabase('users', ['email like' => 'miles%']);

Supported operators: <, >, >=, <=, !=, like.

I think that this section could be moved to Query Generation and a link to Query Generation should be added to docblock of each relevant method - Comparison expressions can be used as well.

What do you think?

Also Since version 2.1.9 is no longer relevant.