You can also perform more complicated updates in Oracle.You may wish to update records in one table based on values in another table.The Oracle UPDATE statement is used to update existing records in a table in an Oracle database.There are 2 syntaxes for an update query in Oracle depending on whether you are performing a traditional update or updating one table with data from another table.Since you can't list more than one table in the Oracle UPDATE statement, you can use the Oracle EXISTS clause. MD_DT DESC) AS ROW_ID FROM t2, t1 WHERE t2.x = 'x' AND t2.y = 'y' AND t2.
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the operation (see Updating Indexes Automatically), so that they remain available throughout.
The book Oracle Tuning: The Definitive Reference notes that if you are still using traditional disks, many shops segregate high-updates objects (tables & indexes) into a separate blocksize so that they can have a separate, small data buffer."By segregating high activity tables into a separate, smaller data buffer, Oracle has far less RAM frames to scan for dirty block, improving the throughput and also reducing CPU consumption.
This is especially important for high update tables with more than 100 row changes per second."The most common issue with updates is the requirement to have a complex SELECT statement is the where clause to identify the rows to be updated.