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Data Manipulation Language (DML)-15

Elsevier Inc.
DOI: 10.1016/b978-155558323-1/50017-6


Publisher Summary This chapter demonstrates the data manipulation language (DML), showing the syntax and plenty of examples. DML commands are used in SQL to add, modify, and remove rows of data in database tables. Transaction control using ROLLBACK and COMMIT commands, among others, plus the MERGE command, are presented. DML is the blanket term for any command that modifies data in an Oracle database. DML commands are usually executed against a single table at a time. The only exceptions to this rule are rare multiple-table inserts, a variation of the INSERT command and the MERGE command. A transaction is a set of one or more SQL commands that change data. A transaction begins when one executes an SQL command, changing something in the database. One can use an optional command called SET TRANSACTION to modify default behavior for a particular transaction. The default transaction setting is READ WRITE, which allows changes and sees other users' changes immediately after being committed. The current transaction can be completed using the COMMIT or ROLLBACK commands. SAVEPOINT is useful when one is making many changes to the database and wants the ability to undo only part of the changes made.

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