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Comparison of Java and .NET platforms ALGOL 58's influence on ALGOL 60; ALGOL 60: Comparisons with other languages; Comparison of ALGOL 68 and C++; ALGOL 68: Comparisons with other languages; Compatibility of C and C++; Comparison of Pascal and Borland Delphi; Comparison of Object Pascal and C; Comparison of Pascal and C; Comparison of Java and C++
The relational algebra uses set union, set difference, and Cartesian product from set theory, and adds additional constraints to these operators to create new ones.. For set union and set difference, the two relations involved must be union-compatible—that is, the two relations must have the same set of attributes.
The EXCEPT ALL operator does not remove duplicates, but if a row appears X times in the first query and Y times in the second, it will appear (,) times in the result set. Notably, the Oracle platform provides a MINUS operator which is functionally equivalent to the SQL standard EXCEPT DISTINCT operator. [3]
Value classes are reference types, in the same way as all existing Java classes. However, they give up the ability to have identity. This means that the == operator compares instance of the value class by equality of their components, instead of by identity. Additionally, synchronizing on instances of value classes will fail.
Some programming languages support a union type for such a data type. In other words, a union type specifies the permitted types that may be stored in its instances, e.g., float and integer . In contrast with a record , which could be defined to contain both a float and an integer; a union would hold only one at a time.
Blocks can be nested – i.e., because a block is an executable statement, it can appear in another block wherever an executable statement is allowed. A block can be submitted to an interactive tool (such as SQL*Plus) or embedded within an Oracle Precompiler or OCI program. The interactive tool or program runs the block once.
A snippet of Java code with keywords highlighted in bold blue font. The syntax of Java is the set of rules defining how a Java program is written and interpreted. The syntax is mostly derived from C and C++. Unlike C++, Java has no global functions or variables, but has data members which are also regarded as global variables.
One common convention is to associate intersection = {: ()} with logical conjunction (and) and associate union = {: ()} with logical disjunction (or), and then transfer the precedence of these logical operators (where has precedence over ) to these set operators, thereby giving precedence over .