SQL Database Concepts Question:
Explain what is the difference between UNION and UNION ALL?
Answer:
UNION selects only distinct values whereas UNION ALL selects all values and not just distinct ones.
UNION: SELECT column_names FROM table_name1
UNION
SELECT column_names FROM table_name2
UNION All: SELECT column_names FROM table_name1
UNION ALL
SELECT column_names FROM table_name2
UNION: SELECT column_names FROM table_name1
UNION
SELECT column_names FROM table_name2
UNION All: SELECT column_names FROM table_name1
UNION ALL
SELECT column_names FROM table_name2
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