1. What is SQL? SQL stands for Structured Query Language, and it is used to communicate with the Database. This is a standard language used to perform tasks such as retrieval, updation, insertion and deletion of data from a database. Basically, it is a database language that is used for the creation and deletion of databases, and it can be used to fetch and modify the rows of a table and also for multiple other things. 2. What are the keys in SQL? A Key is a data item that exclusively identifies a record SQL Server supports various types of keys, which are listed below: Candidate Key Primary Key Unique Key Alternate Key Composite Key Super Key Foreign Key primary key A primary key is a combination of fields which uniquely specify a row. This is a special kind of unique key, and it has implicit NOT NULL constraint. It means, Primary key values cannot be NULL. unique key A Unique key constraint uniquely i...