· SQL refers to "Structured Query Language"
· It is an Structured Query Language because it follows ANSI, ISO standards.
· It is an editor which helps the user to communicate with the Oracle Server.
· User communicates with the help of queries. A query is a request / question / command submitted to oracle server to perform operations over DB.
· SQL is developed by IBM, olden days it was called as “Sequel”.
· It is the language common for all RDBMS software’s like Oracle, SQL Server, MySQL.
· Apart from SQL, we also have QBE and QUEL which are used to communicate with the RDBMS server.
- QBE refers to Query by Example. Used in MS-ACCESS.
- QUEL refers to Query Language.
Depending on the operations, SQL is categorized into following sub languages:
1. DML ( Data Manipulation Language )
2. DDL ( Data Definition Language )
3. DRL ( Data Retrieval Language )
4. TCL ( Transaction Control Language )
5. DCL ( Data Control Language )
Data Definition Language (DDL):
- DDL is a set of instructions to perform operations over Data Definition.
- Data Definition is also called as Metadata. (data about data)
- Commands in DDL are:
(i) CREATE
(ii) ALTER
(iii) DROP
(iv) TRUNCATE
(v) RENAME
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