Types of SQL Statements
The lists in the following sections provide a functional summary of SQL statements and are divided into these categories:
Data Definition Language (DDL) Statements
Data definition language (DDL) statements let you to perform these tasks:
Create, alter, and drop schema objects
Grant and revoke privileges and roles
Analyze information on a table, index, or cluster
Establish auditing options
Add comments to the data dictionary
DROP commands require exclusive access to the specified object. For example, an
TABLE statement fails if another user has an open transaction on the specified table.
COMMENT commands do not require exclusive access to the specified object. For example, you can analyze a table while other users are updating the table.
Oracle Database implicitly commits the current transaction before and after every DDL statement.
A DDL statement is either blocking or nonblocking, and both types of DDL statements require exclusive locks on internal structures.
Oracle Database Development Guide to learn about the difference between blocking and nonblocking DDL
Many DDL statements may cause Oracle Database to recompile or reauthorize schema objects. For information on how Oracle Database recompiles and reauthorizes schema objects and the circumstances under which a DDL statement would cause this, see Oracle Database Concepts.
DDL statements are supported by PL/SQL with the use of the
Oracle Database PL/SQL Packages and Types Reference for more information about this package
The DDL statements are:
ALTER... (All statements beginning with
SYSTEM—see "Session Control Statements" and "System Control Statement")
CREATE... (All statements beginning with
DROP... (All statements beginning with
FLASHBACK... (All statements beginning with
Data Manipulation Language (DML) Statements
Data manipulation language (DML) statements access and manipulate data in existing schema objects. These statements do not implicitly commit the current transaction. The data manipulation language statements are:
SELECT statement is a limited form of DML statement in that it can only access data in the database. It cannot manipulate data stored in the database, although it can manipulate the accessed data before returning the results of the query.
SELECT statement is supported in PL/SQL only when executed dynamically. However, you can use the similar PL/SQL statement
INTO in PL/SQL code, and you do not have to execute it dynamically. The
PLAN statements are supported in PL/SQL only when executed dynamically. All other DML statements are fully supported in PL/SQL.
Transaction Control Statements
Transaction control statements manage changes made by DML statements. The transaction control statements are:
All transaction control statements, except certain forms of the
ROLLBACK commands, are supported in PL/SQL. For information on the restrictions, see COMMIT and ROLLBACK.
Session Control Statements
System Control Statement
The single system control statement,
SYSTEM, dynamically manages the properties of an Oracle Database instance. This statement does not implicitly commit the current transaction and is not supported in PL/SQL.
Embedded SQL Statements
Embedded SQL statements place DDL, DML, and transaction control statements within a procedural language program. Embedded SQL is supported by the Oracle precompilers and is documented in the following books: