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23 Μαΐ 2017 · Here are some use cases for a subquery in the from clause. How it works has been explained in the comments to your question (SQL is mathematical closed thanks to its relational operators). 1. Pivot (SQL Server 2008)
A subquery is a SELECT statement nested inside another statement such as SELECT, INSERT, UPDATE, or DELETE. Typically, you can use a subquery anywhere that you use an expression. Consider this following subquery example that uses the products table from the sample database.
11 Απρ 2022 · From clause can be used to specify a sub-query expression in SQL. The relation produced by the sub-query is then used as a new relation on which the outer query is applied. Sub queries in the from clause are supported by most of the SQL implementations.
23 Οκτ 2017 · According to Using Subqueries Oracle SQL accepts a subquery in the from-clause of a select statement, like. However, looking at the SELECT documentation, I see no possibility to get to select/subquery in the from clause (e.g. from the rules table_reference or join_clause).
You do this by placing the subquery in the FROM clause of the containing query as you would a table name. You may use subqueries in place of tables in this way as well in INSERT , UPDATE , and DELETE statements.
What is a subquery in Oracle? In Oracle, a subquery is a query within a query. You can create subqueries within your SQL statements. These subqueries can reside in the WHERE clause, the FROM clause, or the SELECT clause.
Sub Query in FROM Clause. The following statement selects from subqueries in the FROM clause and for each department returns the total employees and salaries as a decimal value of all the departments. to_char(100*a.num_emp/b.total_count,'990D00') "%_Employees", to_char(100*a.sal_sum/b.total_sal,'990D00') "%_Salary" FROM.
