Introduction to SQL.pptx
- 2. CONTENT What isSQL? SQL Commands DDL Commands DMLCommands DCL Commands DQL Commands
- 3. WHAT ISSQL? Structured QueryLanguage SQL is Structured Query Language, which is a computer langauge for storing, manipulating, and retrieving data stored in relational database. SQL is the standard language for Relation Database System. All relational database management systems like "MySQL, MS Access, Oracle, Postgres and SQL Server" use SQL as standard database language.
- 4. SQL COMMANDS DDL - Data Definition Language DML - Data Manipulation Language DCL - Data Control Language DQL - Data Query Language
- 5. DATA DEFINITIONLANGUAGE (DDL) COMMANDS DDL(Data Definition Language): To make/perform changes to the physical structure of any table residing inside a database, DDL is used. These commands when executed are auto-commit in nature and all the changes in the table are reflected and saved immediately. In SQL DDL commands are used to create and modify the structure of a database and database objects. These commands are CREATE, DROP, ALTER, TRUNCATE, and RENAME. Let us discuss these commands one at a time.
- 6. DATA MANIPULATION LANGUAGE (DML)COMMANDS DML(Data Manipulation Language): Once the tables are created and the database is generated using DDL commands, manipulation inside those tables and databases is done using DML commands. The advantage of using DML commands is, that if in case any wrong changes or values are made, they can be changed and rolled back easily. DML is used for inserting, deleting, and updating data in a database. It is used to retrieve and manipulate data in a relational database. It includes INSERT, UPDATE, and DELETE. Let's discuss these commands one at a time.
- 7. DATA CONTROL LANGUAGE (DCL) COMMANDS DCL(Data Control Language): DCL commands as the name suggests manage the matters and issues related to the data controller in any database. DCL includes commands such as GRANT and REVOKE which mainly deal with the rights, permissions, and other controls of the database system. DCL is used to access the stored data. It is used to revoke and grant the user the required access to a database. In the database, this language does not have the feature of rollback. It is a part of the structured query language (SQL).
- 8. DATA QUERY LANGUAGE (DQL) COMMANDS DQL(Data Query Language): Data query language consists of only one command upon which data selection in SQL relies. The SELECT command in combination with other SQL clauses is used to retrieve and fetch data from databases/tables based on certain conditions applied by the user. DQL commands are used for fetching data from a relational database. They perform read-only queries of data. The only command, 'SELECT' is equivalent to the projection operation in relational algebra. It command selects the attribute based on the condition described by the WHERE clause and returns them.