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PostgreSQL has a distinct BOOLEAN type as in the standard, [21] which allows predicates to be stored directly into a BOOLEAN column, and allows using a BOOLEAN column directly as a predicate in a WHERE clause. In MySQL, BOOLEAN is treated as an alias of TINYINT (1); [22] TRUE is the same as integer 1 and FALSE is the same is integer 0. [23]
Query by Example (QBE) is a database query language for relational databases. It was devised by Moshé M. Zloof at IBM Research during the mid-1970s, in parallel to the development of SQL. [1] It is the first graphical query language, using visual tables where the user would enter commands, example elements and conditions.
User-defined data types are non-primitive types. For example, Java's numeric types are primitive, while classes are user-defined. A value of an atomic type is a single data item that cannot be broken into component parts. A value of a composite type or aggregate type is a collection of data items that can be accessed individually. [6]
IBM Db2 supports boolean values since around 11.1 [2]. Microsoft SQL Server supports storage for booleans using "BIT" data type [citation needed]. MySQL interprets "BOOL" and "BOOLEAN" as a mapping for its native TINYINT(1) type. [3] PostgreSQL provides a standard conforming Boolean type. [4] Oracle Database has proper boolean since Release 23 [5].
A derived table is the use of referencing an SQL subquery in a FROM clause. Essentially, the derived table is a subquery that can be selected from or joined to. The derived table functionality allows the user to reference the subquery as a table. The derived table is sometimes referred to as an inline view or a subselect.
State-based CRDTs (also called convergent replicated data types, or CvRDTs) are defined by two types, a type for local states and a type for actions on the state, together with three functions: A function to produce an initial state, a merge function of states, and a function to apply an action to update a state.
A union type is a special construct that permits access to the same memory block by using a choice of differing type descriptions. For example, a union of data types may be declared to permit reading the same data either as an integer, a float, or any other user declared type:
Major DBMSs, including SQLite, [5] MySQL, [6] Oracle, [7] IBM Db2, [8] Microsoft SQL Server [9] and PostgreSQL [10] support prepared statements. Prepared statements are normally executed through a non-SQL binary protocol for efficiency and protection from SQL injection, but with some DBMSs such as MySQL prepared statements are also available using a SQL syntax for debugging purposes.