DECLAREOPENFETCHCLOSE

DECLAREOPENFETCHCLOSE is not an official SQL command or function, but a concise way to refer to the standard lifecycle of a database cursor in procedural SQL code. The phrase summarizes four core steps used to process a result set row by row: declare the cursor, open it to initialize the result set, fetch rows into variables, and close the cursor to release resources.

The approach is commonly employed inside stored procedures, functions, and scripts where row-by-row processing is required. Declaring a cursor binds a SELECT statement to a cursor name and defines the variables that will receive column values. Opening the cursor initializes the scan and makes the result set available for fetching. Fetch operations retrieve the next row and populate host variables; libraries or languages often provide a status indicator or a condition to signal completion of the result set. Finally, closing (and sometimes deallocating) the cursor releases locks, cursors, and memory resources.

There are dialect differences in how DECLAREOPENFETCHCLOSE is implemented. Some systems require explicit loops around fetch operations and a test for end-of-data, while others offer higher-level constructs that abstract the fetch mechanics with for-each style loops. Proper handling of resources, including ensuring every opened cursor is closed, is a common source of errors, potentially leading to leaks or deadlocks.

Example usage across common systems: in SQL Server, a cursor is declared, opened, and fetched within a WHILE loop, followed by CLOSE and DEALLOCATE. In Oracle and PostgreSQL, explicit OPEN and FETCH are paired with conditions or FOUND/%NOTFOUND checks, or replaced by FOR loops that implicitly manage the cursor. DECLAREOPENFETCHCLOSE thus serves as a shorthand reference to the cursor lifecycle rather than a single command.