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There are several sub-categories of SQL that play specific roles in the querying and manipulation of databases.
| DML | Data Manipulation Language | This set of SQL statements are used to query or change the data stored in the database. DML common statements include SELECT, INSERT, UPDATE, and DELETE. These commands generally only impact rows of data in existing tables. These commands are about "What" data is stored in the database. |
| DDL | Data Definition Language | This set of SQL statements are used to create or modify the structure of the database. "How" is data stored in the database? These commands generally only impact tables and columns and other stored objects in the database. The main statements included in DDL are CREATE, CREATE OR REPLACE, and ALTER. |
| TCL | Transaction Control Language | TCL is a subset of statements that assist in controlling one or more SQL DML statements that need to either completely succeed or entirely fail. A transaction must be complete or not happen at all. Common commands include BEGIN, COMMIT, SAVEPOINT and ROLLBACK |
| PL/SQL | Procedural Language extensions to SQL | PL/SQL is an advanced compiled procedural language extension to SQL that allows for complex processes to be performed on data or databases. PL/SQL contains many of the operations that we would find in most programming languages, such as loops, functions, variables, conditional statements, etc. This topic is not covered until DBS501 or DBS511. |