Relational Databases and SQL

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Relational Databases
The relational model has a structural part (schemata with dependencies) and an operational part (relational algebra). The logical and physical levels are independent of each other. The only basic construct on the logical level is the relation; relations can be illustrated for the users in the form of tables.

SQL (Structured Query Language)
SQL is used to enter and query data in databases and administer databases.

1. SQL was the first SQL developed by IBM during the 1970s.


2. SQL-86 was the first SQL standard adopted by ANSI and ISO.


3. SQL-89 was a minor revision of SQL-86.


4. X/OPEN was an extension of SQL-89.


5. SQL:1992 (SQL2) provided an SQL standard to anticipate future needs.


6. SQL:1999 (SQL3) included object-oriented features.


7. SQL:2003 included XML-related features.


8. SQL:2006 included more XML features such as XQuery.


9. SQL:2008 added INSTEAD OF triggers and the TRUNCATE statement.


10. SQL:2011 added temporal features including valid time and transaction time.


11. SQL:2016 introduced 44 new optional features including JSON and polymorphic table functions.


12. SQL:2019 added multidimensional arrays (MDarray type and operators).


13. SQL:2023 added data type JSON (SQL/Foundation); added Part 16, Property Graph Queries (SQL/PGQ).

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enrollment student_id course_no major 1 101 No 1 108 Yes 2 105 No 3 101 Yes 3 108 No 5 102 No 5 105 No