Usage
To use cursors in SQL procedures, you need to do the following:
- Declare a cursor that defines a result set.
- Open the cursor to establish the result set.
- Fetch the data into local variables as needed from the cursor, one row at a time.
- Close the cursor when done.
To work with cursors you must use the following SQL statements
This section introduces the ways the SQL:2003 standard defines how to use cursors in applications in embedded SQL. Not all application bindings for relational database systems adhere to that standard, and some (such as CLI or JDBC) use a different interface.
A programmer makes a cursor known to the DBMS by using a DECLARE ... CURSOR statement and assigning the cursor a (compulsory) name:
Before code can access the data, it must open the cursor with the OPEN statement. Directly following a successful opening, the cursor is positioned before the first row in the result set.
Programs position cursors on a specific row in the result set with the FETCH statement. A fetch operation transfers the data of the row into the application.
Once an application has processed all available rows or the fetch operation is to be positioned on a non-existing row (compare scrollable cursors below), the DBMS returns a SQLSTATE '02000' (usually accompanied by an SQLCODE +100) to indicate the end of the result set.
The final step involves closing the cursor using the CLOSE statement:
After closing a cursor, a program can open it again, which implies that the DBMS re-evaluates the same query or a different query and builds a new result set.
Read more about this topic: Cursor (databases)
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