Search results
Results From The WOW.Com Content Network
A NOT NULL constraint is functionally equivalent to the following check constraint with an IS NOT NULL predicate: CHECK (column IS NOT NULL) Some relational database management systems are able to optimize performance when the NOT NULL constraint syntax is used as opposed to the CHECK constraint syntax given above. [1]
MySQL (/ ˌ m aɪ ˌ ɛ s ˌ k juː ˈ ɛ l /) [6] is an open-source relational database management system (RDBMS). [6] [7] Its name is a combination of "My", the name of co-founder Michael Widenius's daughter My, [1] and "SQL", the acronym for Structured Query Language.
Reserved words in SQL and related products In SQL:2023 [3] In IBM Db2 13 [4] In Mimer SQL 11.0 [5] In MySQL 8.0 [6] In Oracle Database 23c [7] In PostgreSQL 16 [1] In Microsoft SQL Server 2022 [2]
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 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 other proposals from ...
Unlike a real unit type which is a singleton, the void type lacks a way to represent its value and the language does not provide any way to declare an object or represent a value with type void. In the earliest versions of C, functions with no specific result defaulted to a return type of int and functions with no arguments simply had empty ...
Void safety (also known as null safety) is a guarantee within an object-oriented programming language that no object references will have null or void values. In object-oriented languages, access to objects is achieved through references (or, equivalently, pointers ).
In C, variables with static storage duration that are not initialized explicitly are initialized to zero (or null, for pointers). [ 3 ] Not only are uninitialized variables a frequent cause of bugs, but this kind of bug is particularly serious because it may not be reproducible: for instance, a variable may remain uninitialized only in some ...
Command-query separation (CQS) is a principle of imperative computer programming. It was devised by Bertrand Meyer as part of his pioneering work on the Eiffel programming language . It states that every method should either be a command that performs an action, or a query that returns data to the caller, but not both.