Equal to executable command for main query introduced.
If command introduced.
Query openner partially fixed.
Select commands structure cleared.
Select alias commands from main query distinguish prepend selects.
Removed unused class.
Removed executing from basic "equal to" comparison.
Select commands from main command line are chained with commands of main line as well.
Main command line offers where commands.
Same parts of IS NULL and IS NOT NULL conditions are shared via ancestor.
Same parts of IN and NOT IN conditions are shared via ancestor.
Fixed description of "everything JOIN" situation and added comparison of LIKE and equation conditions.
Same parts of LIKE / NOT LIKE and OR / OR NOT conditions are shared via ancestor.
Conditions added to main query.