This is personal study note
Copyright and original reference:
https://www.youtube.com/watch?v=pSzsX_FaG7o&list=PLVsNizTWUw7HhYtI-4GGmlJ5yxNdwNI_X
================================================================================
LEFT: shows all records of LEFT table
================================================================================
Left table (userTble) shows all records even if those records are not in right table (buyTbl)
================================================================================
================================================================================
Same result but right outer join
================================================================================
Shows the members who didn't buy product
================================================================================
================================================================================
================================================================================
Cross join (cartesian product)
Cross join is meaningless except for the case where you create large data
================================================================================
================================================================================
self join
================================================================================
================================================================================