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SQL:1999 also introduced BOOLEAN type variables, which according to the standard can also hold Unknown values if it is nullable. In practice, a number of systems (e.g. PostgreSQL) implement the BOOLEAN Unknown as a BOOLEAN NULL, which the standard says that the NULL BOOLEAN and UNKNOWN "may be used interchangeably to mean exactly the same thing".
The SQL:1999 standard introduced a BOOLEAN data type as an optional feature (T031). When restricted by a NOT NULL constraint, a SQL BOOLEAN behaves like Booleans in other languages, which can store only TRUE and FALSE values. However, if it is nullable, which is the default like all other SQL data types, it can have the special null value also.
The SQL:1999 standard calls for a Boolean type, [1] but many commercial SQL servers (Oracle Database, IBM Db2) do not support it as a column type, variable type or allow it in the results set. Microsoft SQL Server is one of the few database systems that properly supports BOOLEAN values using its "BIT" data type [citation needed]. Every 1–8 ...
A Boolean value is either true or false. A Boolean expression may be composed of a combination of the Boolean constants True/False or Yes/No, Boolean-typed variables, Boolean-valued operators, and Boolean-valued functions. [1] Boolean expressions correspond to propositional formulas in logic and are a special case of Boolean circuits. [2]
SQL was initially developed at IBM by Donald D. Chamberlin and Raymond F. Boyce after learning about the relational model from Edgar F. Codd [12] in the early 1970s. [13] 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 ...
SQL is a well known query language and data manipulation language for relational databases; XQuery is a query language for XML data sources; XPath is a declarative language for navigating XML documents; YQL is an SQL-like query language created by Yahoo! Search engine query languages, e.g., as used by Google [5] or Bing [6]
In computer science, a Boolean variable is a variable that takes values in some Boolean domain. Some programming languages feature reserved words or symbols for the elements of the Boolean domain, for example false and true. However, many programming languages do not have a Boolean data type in the strict sense.
A command center is a central place for carrying out orders and for supervising tasks, also known as a headquarters, or HQ. Common to every command center are three general activities: inputs, processes, and outputs. The inbound aspect is communications (usually intelligence and other field reports). Inbound elements are "sitreps" (situation ...