Oracle set operation combines two or more result sets into one result set. Result set operations include:
- INTERSECT (intersection) returns the records that are common to the two queries. Select deptno from dept intersect select deptno from emp;
- Union all (UNION set) returns ALL records of each query, including duplicate records. Select deptno from dept union all select deptno from emp;
- UNION (UNION) returns all records of each query, excluding duplicate records. Select deptno from dept UNION select deptno from emp;
- MINUS returns the records retrieved from the first query MINUS the records retrieved from the second query. Select deptno from dept minus select deptno from emp;
When using the set operation, note: the number of columns returned by the query and the column type must be matched, and the column names can be different.
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