SQL
INTERSECT, EXCEPT and Column Compatibility
The two set operations MySQL waited longest to add: rows in both sets, and rows in one set but not the other - plus how to emulate them where they are...
#Set Operations
UNION, INTERSECT and EXCEPT.
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SQL
UNION and UNION ALL
Stacking two result sets on top of each other. Learn the column compatibility rules, why UNION ALL is faster, and where ORDER BY belongs.