A relation is a two-dimensional table. It contains number of rows (tuples) and columns (attributes). A relation has following properties :
(a). In any given column of the table, all items are of the same kind whereas items in different columns may not be of the same kind.
(b). For a row, each coloums must have an atomic value and also for a row, a columns cannot more than one value.
(c). All of a relations are distinct. That is, a relation does not contain two rows which are identical in every column. That is, each row of the relation can be uniquely identified by its contents.
(d). The ordering of two within a relation is immaterial. That is, we cannot retrieved any thing by saying that from row number 5, column name is to be accessed. Thee is no order maintained for rows inside a relation.
(e). The columns of a relation are assigned distinct names and the ordering of these columns is immaterial.
