Both UNION and UNION ALL concatenate the result of two different SQLs. They
differ in the way they handle duplicates.
-UNION performs a DISTINCT on the result set, eliminating any duplicate rows.
-UNION ALL does not remove duplicates, and it therefore faster than UNION.
In ORACLE: UNION does not support BLOB (or CLOB) column types, UNION ALL does.
-UNION performs a DISTINCT on the result set, eliminating any duplicate rows.
-UNION ALL does not remove duplicates, and it therefore faster than UNION.
In ORACLE: UNION does not support BLOB (or CLOB) column types, UNION ALL does.
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