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In computer science, a database cursor is a mechanism that enables traversal over the records in a database. Cursors facilitate processing in conjunction with the traversal, such as retrieval, addition and removal of database records. The database cursor characteristic of traversal makes cursors akin to the programming language concept of iterator.
Cursor-for loops automatically open a cursor, read in their data and close the cursor again. As an alternative, the PL/SQL programmer can pre-define the cursor's SELECT-statement in advance to (for example) allow re-use or make the code more understandable (especially useful in the case of long or complex queries).
I believe that the "disadvantages" section is partly wrong and partly very imprecise. First, cursors are the only way to transfer data from a relational DBMS to a procedural application (with the exception being a SELECT INTO statement). Next, a FETCH does not imply a network round-trip at all - the DBMS client can use block fetch.
A second set is used to send SQL commands from the ODBC system to the DBMS, converting or interpreting any commands that are not supported internally. For instance, a DBMS that does not support cursors can emulate this functionality in the driver. Finally, another set of commands, mostly used internally, is used to convert data from the DBMS's ...
The relational model (RM) is an approach to managing data using a structure and language consistent with first-order predicate logic, first described in 1969 by English computer scientist Edgar F. Codd, [1] [2] where all data are represented in terms of tuples, grouped into relations.
The syntax of the SQL programming language is defined and maintained by ISO/IEC SC 32 as part of ISO/IEC 9075.This standard is not freely available. Despite the existence of the standard, SQL code is not completely portable among different database systems without adjustments.
Object–relational impedance mismatch is a set of difficulties going between data in relational data stores and data in domain-driven object models. Relational Database Management Systems (RDBMS) is the standard method for storing data in a dedicated database, while object-oriented (OO) programming is the default method for business-centric design in programming languages.
Cursor (user interface), an indicator used to show the current position for user interaction on a computer monitor or other display device; Cursor (databases), a control structure that enables traversal over the records in a database; Cursor, a value that is the position of an object in some known data structure, a predecessor of pointers