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MySQL ( / ˌmaɪˌɛsˌkjuːˈɛl /) [5] is an open-source relational database management system (RDBMS). [5] [6] Its name is a combination of "My", the name of co-founder Michael Widenius 's daughter My, [7] and "SQL", the acronym for Structured Query Language.
A query plan (or query execution plan) is a sequence of steps used to access data in a SQL relational database management system. This is a specific case of the relational model concept of access plans. Since SQL is declarative, there are typically many alternative ways to execute a given query, with widely varying performance.
Standard SQL allows two formats for comments: -- comment, which is ended by the first newline, and /* comment */, which can span multiple lines. Queries. The most common operation in SQL, the query, makes use of the declarative SELECT statement. SELECT retrieves data from one or more tables, or expressions.
History. SQL was initially developed at IBM by Donald D. Chamberlin and Raymond F. Boyce after learning about the relational model from Edgar F. Codd in the early 1970s. This version, initially called SEQUEL (Structured English Query Language), was designed to manipulate and retrieve data stored in IBM's original quasirelational database management system, System R, which a group at IBM San ...
The mysqli_query(), mysqli_real_query() and mysqli_multi_query() functions are used to execute non-prepared statements. At the level of the MySQL Client Server Protocol, the command COM_QUERY and the text protocol are used for statement execution. With the text protocol, the MySQL server converts all data of a result sets into strings before ...
Prepared statement. In database management systems (DBMS), a prepared statement, parameterized statement, or parameterized query is a feature where the database pre-compiles SQL code and stores the results, separating it from data. Benefits of prepared statements are: [1] efficiency, because they can be used repeatedly without re-compiling.
History. E. F. Codd mentioned nulls as a method of representing missing data in the relational model in a 1975 paper in the FDT Bulletin of ACM-SIGMOD.Codd's paper that is most commonly cited in relation with the semantics of Null (as adopted in SQL) is his 1979 paper in the ACM Transactions on Database Systems, in which he also introduced his Relational Model/Tasmania, although much of the ...
Hierarchical and recursive queries in SQL. A hierarchical query is a type of SQL query that handles hierarchical model data. They are special cases of more general recursive fixpoint queries, which compute transitive closures . In standard SQL:1999 hierarchical queries are implemented by way of recursive common table expressions (CTEs).