SQL - Introduction

• SQL stands for Structure Query Language. It is also known as SEQUEL.
• In SEQUEL, we use simple English keywords to interact with the database and get information.
• A SQL, is used to create a table or a database. It is also used to store data into the database, also to modify data in database.
• It is also used to manipulate data in the database. We can use truncate, delete, drop data from the database for manipulation.
• A table is a database object which can store the information in the form of rows and columns.
• Table holds user data.
• Every column of the table has a specific datatype.
• Oracle ensures that, the data which is stored is identical with the datatype of the column.
• The SQL language has several parts -
• Data Definition Language(DDL) - It provides commands for defining relation schemas, deleting relations and modifying relation schemas.
• Data Manipulation language(DML) - It provides the ability to query information from the database and to insert tuples into, delete tuples from, and modify tuples in database.
• Integrity - It includes commands for specifying integrity constraints that the data stored in the database must satisfy. Updates that violate integrity constraints are disallowed.
• View Definition - It includes commands for defining views.
• Transaction Control - It includes commands for specifying the beginning and the ending of transaction.