Saturday, January 26, 2013

SQL Questions and Answers

What is SQL?
SQL stands for Structured Query Language. It is a special-purpose programming language designed for managing data in relational database management systems (RDBMS). Most popular SQL commands are "Select", "Insert", "Update", and "Delete".

What is RDBMS?
RDBMS stands for Relational Database Management System. It is a database management system (DBMS) that is based on the relational model as introduced by E. F. Codd, of IBM's San Jose Research Laboratory. Many popular databases such as IBM DB2, MySQL, Microsoft SQL, Oracle currently in use are based on the relational database model.

What is database normalization?
Database normalization is the process of organizing the fields and tables of a relational database to minimize redundancy and dependency. Normalization usually involves dividing large tables into smaller (and less redundant) tables and defining relationships between them. (http://en.wikipedia.org/wiki/Database_normalization)

What is a primary key?  
A primary key is a single field or combination of fields that uniquely defines a record. Primary key can not contain a null value. A table can have only one primary key.

What is a stored procedure?
A stored procedure is a group of Transact-SQL statements compiled into a single execution plan.

What is a trigger? 
A database trigger is a special stored procedure that is automatically executed in response to certain events on a particular table or view in a database. The trigger is mostly used for maintaining the integrity of the information on the database.
Related posts:
SQL Questions and Answers – Part 3
SQL Questions and Answers – Part 2
SQL Questions and Answers – Part 1

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