5.1 DML and DDL

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Unlike other relational databases Oracle Database classifies and separates SQL commands into two distinct groups as shown in Figure 5.1. These two groups are DML or Data Manipulation Language commands, and DDL or Data Definition Language commands. There are two differences between DML and DDL commands:

Figure 5.1: DML Versus DDL

DML commands manipulate data. A DML command is a command that changes column values in rows in tables. Thus the INSERT, UPDATE, DELETE, and MERGE commands are by definition DML commands because they change data. The SELECT statement and the TRUNCATE command are not DML commands. The SELECT statement is not a DML command, it does not change data and as a result does not produce rollback or redo log entries. The TRUNCATE command on the other hand does change data but automatically executes a COMMIT command. The TRUNCATE command is therefore a DDL command.

Now let's take a quick look at syntax for all the Oracle SQL DML statements.

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