1. UNION removes duplicate rows.
“UNION ALL” does not remove the duplicate row. It returns all from all queries.
2. UNION uses a distinct sort.
“UNION ALL” does not use a distinct sort, so the performance of “UNION ALL” is slightly higher than “UNION”.
3. UNION cannot work with a column that has a TEXT data type.
UNION ALL can work with all data type columns.
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