What are cursors?

these cursors are invoked implicitly. User need not create, open, fetch or close the cursor.

these cursors are not invoked implicitly. User needs to create, open, fetch or close the cursor.
Stores a complete copy of the result set. Used mostly where scrolling is required. Static cursors don't support updates.

This cursor supports updates but not scrolling. It supports only fetching serially. Rows are not retrieved from the database until they are fetched.

These are the fastest of the cursors and cannot be updated. They cannot be created on query that returns only read only columns.

It is a scrollable cursor that cannot be updated. These cursors are controlled by a set of physical identifiers called as key set. The keyset is built in a temporary table when the cursor is opened. (More...)

Cursors help us to do an operation on a set of data that we retrieve by commands such as Select columns from table. For example : If we have duplicate records in a table we can remove it by declaring a cursor which would check the records during retrieval one by one and remove rows which have duplicate values. (More...)

Static,
Dynamic,
Forward-only,
Keyset-driven. (More...)

row-by-row processing of the result sets (More...)

Following are different types of cursors available in SQL Server 2005
Base table
Static
Forward-only
Forward-only/Read-only
Keyset-driven
Base table: Base table cursors are the lowest level of cursor available. Base table cursors can scroll forward or backward with minimal cost, and can be updated
Static: Cursor can move to any record but the changes on the data can't be seen.
Dynamic: Most resource extensive. Cursor can move anywhere and all the changes on the data can be viewed.
Forward-only: Cursor moves one step forward, can't move backwards.
Keyset-driven: Only updated data can be viewed, deleted and inserted data cannot be viewed. (More...)

A cursor is a temporary work area created in the system memory when a SQL statement is executed. A cursor contains information on a select statement and the rows of data accessed by it.

This temporary work area is used to store the data retrieved from the database, and manipulate this data. A cursor can hold more than one row, but can process only one row at a time. The set of rows the cursor holds is called the active set. (More...)