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23 Αυγ 2021 · select group_concat( concat( 'select * from `', table_name, '`') separator ' union all ') from `information_schema`.`tables` where `table_name` like 'ft_expenses_%' into @sql; prepare stmt from @sql; execute stmt;
This tutorial shows you how to use the Oracle UNION to combine result sets of multiple queries. The UNION removes duplicate while the UNION ALL does not.
The following statement combines the results of two queries with the UNION operator, which eliminates duplicate selected rows. This statement shows that you must match data type (using the TO_CHAR function) when columns do not exist in one or the other table:
17 Ιαν 2023 · Learn how to use the Union operator in Oracle SQL to combine the results of two or more SELECT statements. This tutorial includes examples and tips for using Union in Oracle SQL with the JustLee book database and a school sample database.
8 Ιουλ 2019 · with employ as (select 1 lev, to_char(d.department_id) emp_id, d.department_name nm, department_id dept_id from departments d union all select 2 lev, to_char(e.employee_id), e.ename nm, e.department_id from employees e) select lev, case when lev = 2 then dept_id end dept, lpad(' ', lev * 4, '.')|| nm nm, emp_id from employ e order by dept_id ...
You can combine multiple queries using the set operators UNION, UNION ALL, INTERSECT, and MINUS. All set operators have equal precedence. If a SQL statement contains multiple set operators, then Oracle evaluates them from the left to right if no parentheses explicitly specify another order.
25 Σεπ 2018 · The Union operator combines the results of two or more queries into a single result set that includes all the rows that belong to all queries in the Union. In simple terms, it combines the two or more row sets and keeps duplicates.
