SQL

 2016. Syntax The SQL language is subdivided into several language elements, including: Clauses, which are constituent components of statements and queries. which says that unquoted names should be folded to upper case. Thus, Foo should be equivalent to FOO not foo according to the standard. Popular implementations of SQL commonly omit support for basic features of Standard SQL, such as the DATE or TIME data types. The most obvious such examples, and incidentally the most popular commercial and proprietary SQL DBMSs, are Oracle. Critics argue that SQL should be replaced with a language that returns strictly to the original foundation: for example, see The Third Manifesto. Orthogonality and completeness Early specifications did not support major features, such as primary keys. Result sets could not be named, and subqueries had not been defined. These were added in 1992. Null The concept of Null is the subject of some debates. The Null marker indicates the absence of a value, and is distinct from a value of 0 for an integer column or an empty string for a text column. The concept of Nulls enforces the 3-valued-logic in SQL, which is a concrete implementation of the general 3-valued logic. This is usually avoided by declaring a primary key, or a unique constraint, with one or more columns that uniquely identifies a row in the table. Impedance mismatch In a similar sense to object–relational impedance mismatch, a mismatch occurs between the declarative SQL language and the procedural languages in which SQL is typically embedded. SQL data types The SQL standard defines three kinds of data types: Constructed types are one of ARRAY, MULTISET, REF, or ROW. User-defined types are comparable to classes in object-oriented language with their own constructors, observers, mutators, methods, inheritance, overloading, overwriting, interfaces, and so on. Predefined data types are intrinsically supported by the implementation. Predefined data types Character types National character types Binary types Numeric types Datetime types Interval type Boolean XML JSON See also Wikibook SQL Object database List of relational database management systems Comparison of relational database management systems Comparison of object–relational database management systems D Query by Example SQL syntax Oracle PL/SQL Microsoft Transact-SQL IBM DB2 Online transaction processing Online analytical processing Data warehouse Relational data stream management system NoSQL MUMPS Hierarchical database model Star schema Snowflake schema Notes References Sources Discussion on alleged SQL flaws C. J. Date with Hugh Darwen: A Guide to the SQL standard : a users guide to the standard database language SQL, 4th ed., Addison Wesley, USA 1997, SQL standards documents ITTF publicly available standards and technical reports The ISO/IEC Information Technology Task Force publishes including SQL. Technical Corrigenda and Technical Reports are published there. Draft documents Formal SQL standards are available from ISO and ANSI for a fee. For informative use, as opposed to strict standards compliance, late drafts often suffice. External links : transcript of a reunion meeting devoted to the personal history of relational databases and SQL. Charles Babbage Institute Collection documents the H2 committee's development of the NDL and SQL standards. Charles Babbage Institute In this oral history Chamberlin recounts his early life, his education at Harvey Mudd College and Stanford University, and his work on relational database technology. Chamberlin was a member of the System R research team and, with Raymond F. Boyce, developed the SQL database language. Chamberlin also briefly discusses his more recent research on XML query languages. This comparison of various SQL implementations is intended to serve as a guide to those interested in porting SQL code between various RDBMS products, and includes comparisons between SQL:2008, PostgreSQL, DB2, MS SQL Server, MySQL, Oracle, and Informix. - An introduction to real-time processing of streaming data with continuous SQL queries Bibliography: Wikipedia @baygross