Database query
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[edit] Database Query
A Database Query is a very broad term used for instructions given to the database to perform certain operations on the data in the database. These operations are usually defined by Relation Algebra in case of Relational Databases. Relational Algebra extends from Relational Calculus.
[edit] Query Languages
[edit] SQL
SQL stands for Structured Query Language. Originally SQL was called SEQUEL and was designed and implemented at IBM Research as an experimental interface to databases. SQL is very comprehensive and is of two types Data Manipulation Language and Data Definition Language.
[edit] DML
DML is used for INSERTING, DELETING or UPDATING Records.
[edit] DDL
DDL is used for retrieving specific data from database.
[edit] Query By Example
Query by Example involves providing an example of the kind of record you expect from the database and the database generates and executes the query for you. [1]
