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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.
23 Αυγ 2016 · I have a table with 18 million rows. I need to do an once-off update to fix a data issue. CREATE TABLE TESTLARGE (CODE number, STATE varchar2 (5), SDATE date, flag char (1)); I have to update the FLAG='Y' based on state and date. UPDATE TESTLARGE SET FLAG='Y' WHERE CODE IN (SELECT CODE FROM TESTLARGE where STATE in ('PRE', 'POST', 'START', 'END
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.
GROUP BY QUERIES. You can group query results on some column values. When you give a SELECT statement without group by clause then all the resultant rows are treated as a single group. For Example, we want to see the sum salary of all employees dept wise. Then the following query will achieved the result
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.
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.
