Types of Oracle SQL Statements

There are six types of Oracle SQL Statements.

1. Data Definition Language (DDL) Statements
2. Data Manipulation Language (DML) Statements
3. Transaction Control Statements
4. Session Control Statements
5. System Control Statements
6. Embedded SQL Statements

What are Data Definition Language (DDL) Statements ?

• DDL statements can neither be rolled back nor need to be committed.
• DDL statements are auto-commit.
• DDL statements create, alter, drop users, objects, database structure and database also.
• for example
• create
• alter
• drop
• Assign or Remove privileges and roles
• for example
• grant
• revoke
• Turn auditing on or off
• for example
• audit
• noaudit
• Empty the table (delete all data from the data and reset high water mark)
• for example
• truncate
• Comments for an objects
• for example
• comment

What are Data Manipulation Language (DML) Statements ?

• DML statements can either be rolled back or commited.
• If a DDL is issued immediately after DML all previous DML transactions are committed.
• i.e. DDL issues a commit or is an auto-commit.
• DML statements are used to query or manipulate data
• Statement to query data
• select
• Statement to add data
• insert
• Statement to manipulate (change) data
• update
• Statement to insert data or update data based on condition
• merge
• Statement to delete data (not truncate)
• delete
• Statement to see execution plan for any of the above DML Statements
• explain plan
• Statement to lock of limit access to an object (table or view)
• lock table

What are Transaction Control Statements ?

• These statements help manage the changes made by DML statements
• Make transaction changes permanent
• commit
• Remove (undo) transaction changes 
• rollback
• Set a save point to undo changes
• savepoint
• Set properties for a transaction
• set transaction

What are Session Control Statements ?

• Session Control Statements allow you to manage and control the properties of a user session.
• Alter current session properties
• alter session
• for example
• data format using
• alter session set NLS_DATE_FORMAT='DD-MON-YYYY HH24:MI:SS'
• enable or disable SQL tracing
• alter session set SQL_TRACE = TRUE;
• alter session set SQL_TRACE = FALSE:
• enable or disable roles for a current session
• set role
• for example
• set role all except data_modify;

What are System Control Statements ?

• System Control Statement are used to change the database instance properties
• alter system
• for example
• Enables you to set system level parameters
• alter system set sec_case_sensitive_logon=true;
• Enables you to terminate a session
• alter system kill session ",;

What are Embedded SQL Statements ?

• Embedded SQL Statements use DDL, DML and Transaction Control Statements within a procedural language (viz : procedure, package, function....)
• They enable you to
• Define, allocate and release cursors
• declare
• open
• close
• Retrieve data from database
• fetch
• Specify a database and connect to it
• declare database
• connect
• Assign variable names
• declare statement
• Initialize descriptors
• describe
• Specify how error and warning conditions are handled
• whenever
• Parse and run SQL statements
• prepare
• execute
• execute immediate

Reference or Source : Various : Oracle documentation, Internet, Personal experience.