What are SQL Statements?

Data System Architecture

About

This article is about statements in a SQL context.

Type

In SQL, there are 4 types of statements:

Type Example
DDL - Data Definition Language Data Dictionary manipulation (create, alter, …)
DML - Data Manipulation Language insert, update, …
QUERY - Select select
TCL - Transaction control commit, rollback

Oracle

Oracle uses also the following names:

  • Session Control Statements (Alter session, Set Role)
  • System Control Statement (Alter System)
  • Embedded Control Statements (Any DML, DDL or TCL that is integrated into a 3GL)

Storage

They are stored in a write ahead log.




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