The origin of SQL and the development of Relational Database go hand-in-hand down the historical path. The relational database concept was developed by Dr.E.F.Codd, an IBM researcher. In June 1970, Dr.Codd published an article entitled"A Relational Model Of Data For Large Shared Data Banks", communication of ACM, Vol.13, No6, Jun 1970, describing his mathematical theory of how data could be stored and maniulated in tables. SQL was conceived in an IBM San Jose research laboratory in mid 1970s as a database Language. - Oracle was earlier called Relational Software, Inc. SQL was completely standardized in 92.
Types of Databases
1) Hierarchical : Mainframe eg: IBM IMS{Information Management System}(1968)
2) Network : Minicomputer eg: DEC and Data General.
3) Relational : PC + Minicaomputer + Mainframe.
NOTE : No DBMS conforms completely to SQL-92
RDBMS meets 12 COdd Rules (published in 1985)
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