__HISTORY OF RELATIONAL MODEL:__

Relational model was 1^{st} proposed by E.F.Codd

System R, then IBM developed it’s own DB known as DB2, then Oracle was created

Relation s actually the mathematical table.

__RELATIONAL DATASTRUCTURES__** /STRUCTURAL PART OF **

**RELATION/ TERMINOLOGY**

**Relation**: a table wth Col & rows.**Attribulte**/fields : named column**Tuple**: row of relation/record**Degree**:num of att in a relation .if the colum/attr is only one then relation s of degree- one also known as uniary . if a relation has two columns then it’s knowm as degree 2 also
- known as binary.
**Cardinality**: num of rows (tuple) in a relation .**Domain**: data type .Set of allowable values for one or more att.**Relational****Db**: collection of normalized relations.

__PROPERTIES OF RELATION:__

- Each table should have a distinct name.
- Each cell should have one value (atomic value).
- Attribute names should be unique.
- Values of an attr are from the same domain.
- Order of att has no significance.
- Each tuple should be distinct. Means no duplicate rows.
- Order of rows has no sigificance