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8 lis 2010 · Using UNION automatically removes duplicate rows unless you specify UNION ALL: http://msdn.microsoft.com/en-us/library/ms180026(SQL.90).aspx
The UNION operator selects only distinct values by default. To allow duplicate values, use UNION ALL: SELECT column_name (s) FROM table1. UNION ALL. SELECT column_name (s) FROM table2; Note: The column names in the result-set are usually equal to the column names in the first SELECT statement.
Każde z zapytań biorących udział w operacji łączenia zbiorów zwraca w wyniku zdublowane wartości elementów (nie usuwamy ich za pomocą DISTINCT), robi to domyślnie operator UNION – czyli dostajemy tylko unikalne wartości elementów zbioru (A + B) – USA i UK.
19 wrz 2018 · In this post, I am going to show you a tricky method of removing duplicate rows using traditional UNION operator. In my earlier post on SQL SERVER – Delete Duplicate Rows, I showed you a method of removing duplicate rows with the help of ROW_NUMBER() function and COMMON TABLE EXPRESSION.
17 lip 2024 · MySQL używa klauzuli DISTINCT jako domyślnej podczas wykonywania zapytań UNION, jeśli nic nie jest określone. Klauzula ALL służy do zwrócenia wszystkich, nawet zduplikowanych wierszy w zapytaniu UNION.
The UNION ALL command combines the result set of two or more SELECT statements (allows duplicate values). The following SQL statement returns the cities (duplicate values also) from both the "Customers" and the "Suppliers" table: Example. SELECT City FROM Customers. UNION ALL. SELECT City FROM Suppliers. ORDER BY City; Try it Yourself »
18 cze 2024 · What Is UNION Operation. The UNION operation in SQL combines the results of two or more SELECT queries into a single distinct result set. It removes duplicate rows from the final result, ensuring each row appears only once. The basic syntax for the UNION operation is: SELECT column1, column2, column3. FROM table1.
