<ul><li>UNION combines the results of two or more SELECT statements into a single result set and removes duplicate rows.</li><li>UNION ALL also combines the results of two or more SELECT statements into a single result set, but retains all rows, including duplicates.</li><li>UNION performs an implicit DISTINCT operation to remove duplicates, which can be slower for large datasets.</li><li>UNION ALL is faster than UNION since no duplicate-checking occurs.</li></ul>

SQL UNION vs UNION ALL: Key Differences Explained

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