Celebrating 50 Years of Diversity and Inclusion.Research Departments, Centers, Initiatives and more.Scripting on this page enhances content navigation, but does not change the content in any way. MINUS ExampleВ The following statement combines results with the MINUS operator, which returns only unique rows returned by the first query but not by the second: INTERSECT ExampleВ The following statement combines the results with the INTERSECT operator, which returns only those rows returned by both queries: The UNION ALL operator does not eliminate duplicate selected rows:ДЄ location_id value that appears multiple times in either or both queries (such as ' 1700') is returned only once by the UNION operator, but multiple times by the UNION ALL operator. UNION ALL ExampleВ The UNION operator returns only distinct rows that appear in either result, while the UNION ALL operator returns all rows. SELECT location_id, TO_CHAR(NULL) 'Department', warehouse_name TO_CHAR(NULL) 'Warehouse' FROM departments SELECT location_id, department_name 'Department', This statement shows that you must match datatype (using the TO_CHAR function) when columns do not exist in one or the other table: UNION ExampleВ The following statement combines the results of two queries with the UNION operator, which eliminates duplicate selected rows. Therefore, you should use parentheses to specify order of evaluation in queries that use the INTERSECT operator with other set operators. To comply with emerging SQL standards, a future release of Oracle will give the INTERSECT operator greater precedence than the other set operators. You cannot use these operators in SELECT statements containing TABLE collection expressions. You cannot specify the order_by_clause in the subquery of these operators. You cannot also specify the for_update_clause with the set operators. If the select list preceding the set operator contains an expression, then you must provide a column alias for the expression in order to refer to it in the order_by_clause. The UNION, INTERSECT, and MINUS operators are not valid on LONG columns. The set operators are not valid on columns of type BLOB, CLOB, BFILE, VARRAY, or nested table.

Restrictions on the Set OperatorsВ The set operators are subject to the following restrictions: This is implicitly converted to the following compound query: See Also: Table 2-10, 'Implicit Type Conversion Matrix' for more information on implicit conversion and 'Numeric Precedence' for information on numeric precedence Therefore, if the corresponding expressions of component queries resolve to both character data and numeric data, Oracle returns an error. In queries using set operators, Oracle does not perform implicit conversion across datatype groups. If all queries select values of type NUMBER, then the returned values have datatype NUMBER. If no query selects values of type BINARY_DOUBLE but any query selects values of type BINARY_FLOAT, then the returned values have datatype BINARY_FLOAT. If any query selects values of type BINARY_DOUBLE, then the returned values have datatype BINARY_DOUBLE. If component queries select numeric data, then the datatype of the return values is determined by numeric precedence: If either or both of the queries select values of datatype VARCHAR2, then the returned values have datatype VARCHAR2. If the queries select values of CHAR with different lengths, then the returned value is VARCHAR2 with the length of the larger CHAR value. If both queries select values of datatype CHAR of equal length, then the returned values have datatype CHAR of that length. If component queries select character data, then the datatype of the return values are determined as follows: The corresponding expressions in the select lists of the component queries of a compound query must match in number and must be in the same datatype group (such as numeric or character). If a SQL statement contains multiple set operators, then Oracle Database evaluates them from the left to right unless parentheses explicitly specify another order. You can combine multiple queries using the set operators UNION, UNION ALL, INTERSECT, and MINUS.

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