SQL
SQL is Structured Query Language standard RDMS language. All relational database management systems like MySQL, MS Access, Oracle, Sybase, Informix, postgres and SQL Server use SQL as standard database language.
Why SQL?
For the following task
- Querying data.
- Insert, update, and delete.
- Create, replace, alter and drop.
- Controlling access to database.
- Grantee database consistency and integrity.
Features
- Automatic navigation to the data.
- Process the set of data rather than single or individual unit.
Basic Elementing of SQL
- Data Type
- Database object
- Operation
- Expression
- Funtion
- Condition
- Data Type
Each value manipulated in SQL has datatype.
Data type categorized as,
- Built in Datatype
- User defined Datatype
Built in Datatype
- varchar
- number
- long
- date
- float
- int
- raw
- blob
- lob
- nblob
- blob raw
- blob long raw
2. Database Object
Object associated with a particular schema which is collection of logical data structure.
Schema Object
- table
- view
- trigger
- index
- constraint
- function
- procedure
Non Schema Object
- directories
- restore pointer
- user
- tablespace
- rollback
- segment
- rules
What is Table?
Collection of related data in form of rows and columns.
The Data store in database object is called table.
Name is unique for each table.
No. of attribute is DEGREE.
No. of tuple a relation is CARDINALITY.
SQL Commands
Commands interact with database.
They are following types,
- Data Definition Language -DDL
- Data Manipulation Language - DML
- Data Translation Language - DTL
- Data Query Language - DQL
- Data Control Language - DCL
