The first databases implemented during the 1960s and 1970s were based upon either flat data files or the hierarchical or networked data models. These methods of storing data were relatively inflexible due to their rigid structure and heavy reliance on applications programs to perform even the most routine processing. In the late 1970s, the relational database model which originated in the academic research community became available in commercial implementations such as IBM DB2 and Oracle. The data stored in each column must be of a single data type such as Character, Number or Date. A collection of values from each column of a table is called a record or a row in the table.
Different tables can have the same column in common.
This feature is used to explicitly specify a relationship between two tables. Values appearing in column A in one table are shared with another table. Mrs. Jones 12 Davis Ave. Mr. Axe 443 Grinder Ln. The data type for a column indicates the type of data values that may be stored in that column.