Αποτελέσματα Αναζήτησης
If you want to update specific rows (ie where the IDs match) you probably want to do a coordinated subquery. However, since you are using Oracle, it might be easier to create a materialized view for your query table and let Oracle's transaction mechanism handle the details.
6 Δεκ 2017 · Learn about several methods to update data using subqueries in UPDATE statements to make them more effective and easier to maintain in Oracle SQL.
Subquery Method. The first option is to do an update of the DEST_TAB table using a subquery to pull the correct data from the SOURCE_TAB table. Notice the EXISTS predicate to exclude rows from the DEST_TAB table with no matching row in the SOURCE_TAB table.
2 Ιουν 2023 · 5 – Update with Subquery. Works with: Oracle, SQL Server, MySQL, PostgreSQL. Another way to update a table based on a Select query from another table is to use a subquery. UPDATE person SET account_number = ( SELECT account_number FROM account WHERE account.person_id = person.person_id );
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.
Oracle performs a correlated subquery when a nested subquery references a column from a table referred to a parent statement one or more levels above the subquery or nested subquery. The parent statement can be a SELECT, UPDATE, or DELETE statement in which the subquery is nested.
You can use the flashback_query_clause within the subquery to update table with past data. Refer to the flashback_query_clause of SELECT for more information on this clause.
