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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.
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.
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.
This page describes how to write SQL to update a table using a subquery in PL/SQL.
30 Μαΐ 2011 · From Oracle Database 23ai you can use direct joins in update to copy values from one table to another:
Specify the name of the table, view, materialized view, or the columns returned by a subquery to be updated. Issuing an UPDATE statement against a table fires any UPDATE triggers associated with the table. If you specify view, then the database updates the base table of the view.
Update using correlated subquery. This statement uses a correlated subquery to update a single column across multiple rows in the FLIGHTS table. It increases the duration of all BA flights by thirty minutes. The subquery returns all flights with OPERATING_CARRIER_CODE set to 'BA'. This result is used as the predicate value in the UPDATE statement.
