Introduction To SQL
Sub Queries in SQL
A subquery is a query whose results are passed as the argument for another query. Sub queries enable us to bind several queries together.
Data Definition Language
A data definition language (DDL) is a computer language used to create and modify the structure of database objects in a database. These database objects include views, schemas, tables, indexes, etc. This term is also known as data description language in some contexts, as it describes the fields and records in a database table.
Data Manipulation Language
A DML or refers to a computer programming language that allows you to add, delete, and alter data in a database. A DML is typically a sub language of a larger database language like SQL, with the DML containing some of the language's operators.
Security and Access
Data Control Statements are used for authorizing data access, in order to preserve the security of the data within the database. These statements can ensure that unauthorized users don’t change or view data accidentally or deliberately. Data access authorizations are provided using the GRANT statement.
Integrity Constraints
An integrity constraint is a declarative way to define a business rule for a column of a table. An integrity constraint is a statement about a table's data that is always true.