What is the difference between UNION and UNION ALL in SQL?

Question

Accepted Answer

SQL UNION combines results from multiple queries, while UNION ALL includes duplicates.

UNION removes duplicate records from the result set.
UNION ALL includes all records, even duplicates.
Example of UNION: SELECT column1 FROM table1 UNION SELECT column1 FROM table2;
Example of UNION ALL: SELECT column1 FROM table1 UNION ALL SELECT column1 FROM table2;
Use UNION when you want distinct results; use UNION ALL for performance with large datasets.

Accepted Answer

union remove duplicates and union all does not remove duplicates.

Accepted Answer

UNION only returns a unique record, while UNION ALL returns all the records (including duplicates

Accepted Answer

UNION removes duplicates whereas UNION ALL doesnot.

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