![]() The UNION operator does not allow any duplicates. The managers are labeled as “Manager” and their subordinates as “Employee” in the temporary “Type” column of the UNION result.Īliases help in creating organized table results. ![]() The following is the result of the above query: In the above query, we’ve created a temporary column labeled as “Type,” which will be used to categorize the information as employee or manager information. We use the “AS” operator to create aliases.įor example, we’ll use the following query to retrieve all the employees’ and managers’ information, and we’ll categorize them according to their roles. These aliases exist only for the duration of the query they are being used in. SQL aliases are temporary names given to tables or columns. To find the names and addresses of all managers in the dataset and all the employees having “Dept_ID” equal to 1003: We can also use the WHERE clause in only one of the SELECT statements in the UNION.To retrieve employee and manager names and salaries that exceed 60,000 from the “Employee_dept” and “Manager” tables, we’ll input the following:.We can use the WHERE clause in either one or both of the SELECT statements to filter out the rows being combined. Using the Where Clause With the UNION Operator We can also filter the rows being retrieved by each SELECT statement. The result is sorted according to the “Dept_ID.” To retrieve the name and department of each employee and manager from the two sample tables above, you’ll use the following code: We can apply UNION on multiple columns and can also order the results using the ORDER BY operator in the end. The result column's name is “City,” as the result takes up the first SELECT statement’s column names. This shows that no copies are present in the result. To determine which cities the employees and managers belong to from the two tables above, we’ll use the following query: Let’s use the following table, “Employee_dept,” as an example: Let’s apply this operator to different tables’ columns. The columns must be in the correct order in the SELECT statements.For example, “char” and “varchar” are identical data types. The columns in the same position in each SELECT statement should have similar data types.The number of columns being retrieved by each SELECT command, within the UNION, must be the same.
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