Why cursor is used in db2

A hold cursor allows uninterrupted access to a set of rows across multiple transactions. Ordinarily, all cursors close at the end of a transaction.

A hold cursor does not close; it remains open after a transaction ends. What happens if cursor is not closed in DB2? When program ended, it automatically closes the cursor. OPen command will fail. What is the use of cursor in Cobol? The syntax is like below. A cursor is opened for storing data retrieved from the result set. Fetching Cursor. When a cursor is opened, rows can be fetched from the cursor one by one or in a block to do data manipulation. Closing Cursor.

The cursor should be closed explicitly after data manipulation. Cursors are used by database programmers to process individual rows returned by database system queries. In SQL procedures, a cursor makes it possible to define a result set a set of data rows and perform complex logic on a row by row basis. It is better to close all cursors explicitly, however. For Select or Function cursors, this action simply makes the intent of the program clear.

To open a cursor, it is required to declare it first. It is still, however, a good idea to explicitly close the cursor yourself. And if it is local, then including a CLOSE statement will also show other developers and your manager that you are paying attention.

When a cursor is opened, the following things happen: The values of the bind variables are examined.

Based on the values of the bind variables, the active set the query result is determined. The active set pointer is set to the first row. Every emphasis of the loop will be executed inside system memory and consuming required server assets. Cursor Life Cycle Practical Example.

Why Cursor? We can use the cursor in two places to retrieve the data, and those are - Application program DB2 stored procedure Here, we will discuss the application program with the cursor concept. The application program process the rows at a time. Cursor Life Cycle - The cursor plays a very important in retrieving the rows one by one from the result table.

The cursor life cycle has the following phases - Phase Description Declare Cursor Declares a cursor in the application program. Open Cursor Opens the cursor declared in the application program. Close Cursor Closes the cursor specified with it. It is also read-only if the FROM clause identifies a read-only view or identifies more than one table or view. This is a particular problem when a file of updates has a particular order to its records and you would like to code an ORDER BY clause so a merge can be performed.

The cursor will remain open and positioned on the current row in the cursor at the time of commit. Readies the cursor for row retrieval. OPEN is an executable statement. This table is placed in Virtual Storage. It does not assign values to host variables, though. Returns data from the results table one row at a time and assigns the values to specified host variables. You can let DB2 automatically close the cursor when the application program terminates but this practice is not recommended.

Only one row is updated, the current row.