SQL is the world’s most widely used database query language. It was developed at IBM Research Laboratories in the 1970s, based on the relational data model defined by E. F. Codd in 1970. It supports retrieval, manipulation, and administration of data stored in tabular form. It is the subject of an international standard named Database Language SQL.
Early Language Development
In June 1970, E. F. Codd of IBM Research published a paper  defining the relational data model and introducing the concept of data independence. Codd’s thesis was that queries should be expressed in terms of high-level, nonprocedural concepts that are independent of physical representation. Selection of an algorithm for processing a given query could then be done by an optimizing compiler, based on the access paths available and the statistics of the stored data; if these access paths or statistics should later change, the algorithm...
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