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The UNION operator is used to combine the result-set of two or more SELECT statements. Every SELECT statement within UNION must have the same number of columns. The columns must also have similar data types. The columns in every SELECT statement must also be in the same order.
Introduction to Oracle UNION operator. The UNION operator is a set operator that combines result sets of two or more SELECT statements into a single result set. The following illustrates the syntax of the UNION operator that combines the result sets of two queries: SELECT . column_list_1. FROM . T1. UNION SELECT . column_list_1. FROM . T2;
FROM . table1 . UNION [ALL] SELECT . column3, column4. FROM . table2; Code language: SQL (Structured Query Language) (sql) To use the UNION operator, you write the dividual SELECT statements and join them by the keyword UNION. The columns returned by the SELECT statements must have the same or convertible data type, size, and be the same order.
The UNION operator returns only distinct rows that appear in either result, while the UNION ALL operator returns all rows. The UNION ALL operator does not eliminate duplicate selected rows:
1 Οκτ 2024 · The UNION operator is used to combine the results of the two SELECT statements and remove duplicate rows. The first SELECT statement selects prod_code and prod_name from the product table. The second SELECT statement selects prod_code and prod_name from the purchase table.
24 Ιουλ 2024 · The SQL UNION operator combines the result sets of two or more SELECT queries. UNION returns unique rows, eliminating duplicate entries from the result set. UNION ALL includes all rows, including duplicate rows. Columns in the result set must be in the same order and have the same data types.
Syntax: SELECT expr_1, expr_2, ... expr_n FROM table1 WHERE conditions UNION SELECT expr_1, expr_2, ... expr_n FROM table2 WHERE conditions; Parameters: expr_1, expr_2, … expr_n: It is used to specify the columns of the table which needs to be retrieved.
