SQL stands for Structured Query Language and is a widely used programming language for interacting with databases. It is used to query insert update and delete data from databases.SQL statements can be classified into three categories: DDL (Data Definition Language) DML (Data Manipulation Language) and DCL (Data Control Language). DDL statements are used to create and modify database objects such as tables views and stored procedures. DML statements are used to query insert update and delete data from database tables. DCL statements are used to control access to database objects and data.A database table is a collection of data that is organized into rows and columns. Tables are used to store data in a relational database.4 What is a primary key A primary key is a column or SQL is a standard programming language for accessing and manipulating databases. The basic SQL commands are SELECT INSERT UPDATE DELETE and CREATE TABLE. A primary key is a column or set of columns in a table that uniquely identify each row in the table. Primary keys must contain unique values and cannot be NULL. A foreign key is a column or set of columns in a table that matches the primary key of another table. Foreign keys can be NULL.SQL or Structured Query Language is a computer language designed for managing data held in relational databases. SQL is used by database administrators to create update and delete databases and by developers to querying data from databases. DDL (Data Definition Language) statements are used to create modify or delete database objects such as tables indexes or views. DML (Data Manipulation Language) statements are used to insert update or delete data from database tables. DCL (Data Control Language) statements are used to grant or revoke permissions on database objects.A primary key is a column (or set of columns) in a table that uniquely identify each row in the table. A primary key can not be NULL and must be unique for each row. A table can have only one primary key