Cursors in SQL are used to retrieve and manipulate data one row at a time and we are often used them in situations where it is necessary to process the data row by row. Cursors are useful when working with large datasets or when performing complex calculations on the data.In SQL, a cursor is a mechanism that allows for the traversal and manipulation of the rows in a result set returned by a SELECT statement. A cursor can be used to retrieve data row-by-row and perform various operations on each row, such as updating or deleting the data.While cursors may seem like a good idea, they can often cause your database application problems as they are slow, and can lock the tables that are used to populate the cursor while the rows in the cursor are looped through. In any case, it is always good to have the cursor knowledge when you want or need to use one.
What is the purpose of cursor object in SQL : A cursor is a data access object that can be used to either iterate over the set of rows in a table or insert new rows into a table. Cursors have three forms: search, insert, and update. Cursors are commonly used to read existing geometries and write new geometries.
Why use cursor instead of select
Cursors enable an application to retrieve and manipulate individual rows without the restriction of the select loop. Within a select loop, statements cannot be issued that access the database. Use cursors in the following situations: When a program needs to scan a table to update or delete rows.
What are the benefits of cursor : Cursors allow a client application to access individual rows within a result set, rather than merely retrieve a complete set of data rows. A single connection can have multiple cursors open at the same time.
What are cursors used for Cursors are often used to highlight text or objects on the screen so that they can be selected. For example, in a word processor, the cursor can be used to select text, format it, and insert new text. Users control cursors with input devices such as mice, touchpads and trackballs.
Cursors allow a client application to access individual rows within a result set, rather than merely retrieve a complete set of data rows. A single connection can have multiple cursors open at the same time.
Why do we need cursor in Oracle
To execute a multi-row query, Oracle opens an unnamed work area that stores processing information. A cursor lets you name the work area, access the information, and process the rows individually.Advantages and Disadvantages of Cursor in Oracle
- The Cursor fetches the data Row wise, so Row Wise validation is possible using the Cursor.
- It retrieves one row at a time, unlike SQL select query, which selects all rows simultaneously.
- The While Loop is faster than it but does have more overhead.
Cursors are used to fetch single rows from the result set returned by a query and allow the row-by-row iteration through the result set, whereas set based processing can be much faster. Cursors can also cause transactional problems because of the run time.
In conclusion, cursors in SQL can be a helpful tool for handling complex queries requiring individual row processing or executing a stored procedure or trigger for each row. However, they can also have some drawbacks, such as decreased efficiency and potential locking issues in a multi-user environment.
Should I use a cursor : Therefore, you should use cursors and loops sparingly, and only when set-based operations are not feasible or efficient.
What is the disadvantage of using cursor : Disadvantages of Cursor in SQL
Cursors in SQL have certain disadvantages that developers should consider when using them: Performance Overhead: Cursors can incur significant performance overhead, especially with large result sets, as individual fetch operations can be time-consuming.
Why are SQL cursors slow
cursors can be slow and memory—intensive because each time a cursor fetches a row, it also creates a copy of it in memory (leading to an expensive consumer of resources); poorly written cursors can “devour” your available memory.
Cursors allow a client application to access individual rows within a result set, rather than merely retrieve a complete set of data rows. A single connection can have multiple cursors open at the same time.Response time Cursors can provide the first few rows before the whole result set is assembled. If you do not use cursors, the entire result set must be delivered before any rows are displayed by your application.
Why use cursor instead of SELECT : Cursors enable an application to retrieve and manipulate individual rows without the restriction of the select loop. Within a select loop, statements cannot be issued that access the database. Use cursors in the following situations: When a program needs to scan a table to update or delete rows.