If you pass a null to the where array of update or delete it's
pretty obvious what you want.

Most (all?) databases won't match anything if you actually try
to compare with NULL making this a silent failure without it.

The param comment is currently set to string, which is wrong.
The correct hint would be integer/int

1. Reworked the parser syntax to use proper Oracle escaping syntax as '' instead of \'.
2. Moved valid tests to the Functional section to ensure correct SQL syntax and logic.

Single drivers get and return various types in quote(), the
interface docs should reflect that.

Closes #1882

primary key on MySQL platform.

Default isolation level on mysql is REPEATABLE READ

https://dev.mysql.com/doc/refman/5.7/en/server-system-variables.html#sysvar_tx_isolation