- SQL: by name is Structured Query Language is a programming
language, than a protocol, used in the communications between
clients and servers.
It is an ANSI (American National Standards Institute) standard which can query and retrieve data from a database. The database vendors adhere to this standards. - SQL provides a abstract view of data stored in the databases.
- SQL client does not have to know how the data is organized in order to access it.
- Database Relational Model : The relational data model are based
on the tuples, meaning unordered sets of known values with names.
a=apple, b=banana, c=citrus
a=axis, b= branch , c=cat.
a=answer, b =boy, c= cow
a b c apple banana citrus axis branch cat answer boy cow In the above three columns and rows, the contents have have some analytical or logical relationship. Usually a row contains a set of adjacent-fields which would represent properties of an item.
First-name Last-Name Age John Doe 45 Jane Lee 21 Peter Pan 12 In the above setup, each field in a column has logical pattern or arrangements, where as each field in a row has phenotypic relation. Each row collectively called a record and segregated from another row with a rule of separation.
- SQL is non procedural language: Unlike C/C++, Java or PHP , SQL is declarative and non-procedural language
- A Virtual Table or View is a representation of actual table. : SQL language creates a temporary table with the data stored in a base table
Both ANSI and the ISO/IEC have accepted SQL as the standard language for relational databases.