A cursor in SQL is a database object stored in temp memory and used to work with datasets. You can use cursors to manipulate data in a database, one row at a time. A cursor uses a SQL SELECT statement to fetch a rowset from a database and then can read and manipulate one row at a 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.A database cursor is an identifier associated with a group of rows. It is, in a sense, a pointer to the current row in a buffer. You must use a cursor in the following cases: Statements that return more than one row of data from the database server: A SELECT statement requires a select cursor.
What is cursor and view in SQL : A view is a virtual table that gives logical view of data from base table. A CURSOR (CURrent Set of Records) is a temporary workstation created in the database server when the SQL statement is executed.
Why use cursor in SQL
In SQL procedures, a cursor make it possible to define a result set (a set of data rows) and perform complex logic on a row by row basis. By using the same mechanics, an SQL procedure can also define a result set and return it directly to the caller of the SQL procedure or to a client application.
How do I create a cursor in SQL : In SQL, a cursor is declared using the DECLARE statement followed by the cursor name, CURSOR, its scope, and type of cursor followed by a SELECT statement. The SELECT statement selects rowset from the database. Here is the complete syntax of declaring a cursor.
In SQL procedures, a cursor make it possible to define a result set (a set of data rows) and perform complex logic on a row by row basis. By using the same mechanics, an SQL procedure can also define a result set and return it directly to the caller of the SQL procedure or to a client application.
In addition, Explicit cursors are specifically useful while dealing with large amounts of data and also performing complex operations on each row. Thus, they enable the programmer to process the data one row at a time. This can improve performance and reduce memory usage.
What is MySQL cursor
A cursor in MySQL is an iterator used to store the variables in a stored procedure. It helps us to iterate through a result given by a query. Results are in the form of a set of rows, and MySQL cursor help to process each row one at a time.Implicit cursors are the system-defined cursors, and explicit cursors are the user-defined. Triggers are the scheduled procedures executed automatically when an event is fired. Triggers are configured and are then automatically executed by the DBMS engine without writing and executing any further program.In SQL Server, a cursor is a database object that allows us to retrieve and manipulate each row one at a time. A cursor is nothing more than a row pointer. It is always used alongside a SELECT command in SQL. It is typically a set of SQL logic that loops through a set number of rows one by one.
A cursor in SQL is a database object that allows you to retrieve and manipulate data one row at a time. Cursors are typically used when performing operations on each result set row, such as updating or deleting.
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.
How do I create a cursor : The first step is to declare the cursor using the below SQL statement:
- DECLARE cursor_name CURSOR FOR select_statement;
- OPEN cursor_name;
- FETCH NEXT FROM cursor INTO variable_list;
- WHILE @@FETCH_STATUS = 0 BEGIN FETCH NEXT FROM cursor_name; END;
- CLOSE cursor_name;
- DEALLOCATE cursor_name;
Why cursor is not recommended in SQL
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.
Cursor process
- Associate a cursor with the result set of a Transact-SQL statement, and define characteristics of the cursor, such as whether the rows in the cursor can be updated.
- Execute the Transact-SQL statement to populate the cursor.
- Retrieve the rows in the cursor you want to see.
A trigger is a procedure (code segment) that is executed automatically when some specific events occur in a table/view of a database, while a cursor is a control structure used in databases to go through the database records. A cursor can be declared and used within a trigger.
Is a cursor better than a while loop : cursors can be faster than a while loop but at the cost of more overhead. quite flexible. you don't necessarily need a condition to run — the cursors have a row-by-row execution, and you handle a set of rows as a record.