Question: What does cursor do in SQL?

A SQL Server cursor is a set of T-SQL logic to loop over a predetermined number of rows one at a time. The purpose for the cursor may be to update one row at a time or perform an administrative process such as SQL Server database backups in a sequential manner.

What is a SQL cursor used for?

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.

Is it good to use cursor in SQL?

Cursors could be used in some applications for serialized operations as shown in example above, but generally they should be avoided because they bring a negative impact on performance, especially when operating on a large sets of data.

IT IS IMPORTANT:  Does SQL stand for?

When should we use cursor in SQL Server?

In SQL server, a cursor is used when you need Instead of the T-SQL commands that operate on all the rows in the result set one at a time, we use a cursor when we need to update records in a database table in a singleton fashion, in other words row by fetch one row at a time or row by row.

What is the role of a cursor?

In computer user interfaces, a cursor is an indicator used to show the current position for user interaction on a computer monitor or other display device that will respond to input from a text input or pointing device. The mouse cursor is also called a pointer, owing to its resemblance in usage to a pointing stick.

What is the advantage of cursor?

Advantages of using Cursor:

Cursors can provide the first few rows before the whole result set is assembled. Without using cursors, the entire result set must be delivered before any rows are displayed by the application. So using cursor, better response time is achieved.

When would you use a cursor?

Cursors are useful when 1) you need to do something that you cannot do with a set operation, or 2) it doesn’t make sense to do the same work by making iterative calls from the application layer.

Why cursor is bad for performance?

Because cursors take up memory and create locks. What you are really doing is attempting to force set-based technology into non-set based functionality.

Is cursor slow in SQL?

–This is the start of the cursor loop. This cursor will fetch exactly the same set of data but it does it on a row by row basis, and it takes heck of a lot longer to do so, as a matter of fact 48 seconds as opposed to 87 milliseconds, that’s 55172% slower!

IT IS IMPORTANT:  Why Java applets are dead?

What is a cursor in database?

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. … Statements that return more than one row of data from the database server: A SELECT statement requires a select cursor.

What is cursor explain with example?

A cursor is a temporary work area created in the system memory when a SQL statement is executed. … 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. There are two types of cursors in PL/SQL : Implicit cursors.

What is the difference between cursor and while loop in SQL Server?

Loop and cursor can be utilized in a circumstance to deal with row-based processing in T-SQL. … While SQL While loop is quicker than a cursor, reason found that cursor is defined by DECLARE CURSOR. Every emphasis of the loop will be executed inside system memory and consuming required server assets.

How do I view a cursor in SQL?

Difference between View and Cursor in SQL :

  1. Declare the cursor in declaration section.
  2. Open the cursor in execution section.
  3. Fetch the cursor to retrieve data into PL/SQL variable.
  4. Close the cursor to release allocated memory.

What is cursor in Oracle SQL?

A cursor is a pointer to this context area. … PL/SQL controls the context area through a cursor. A cursor holds the rows (one or more) returned by a SQL statement. The set of rows the cursor holds is referred to as the active set.

IT IS IMPORTANT:  Your question: How do I select a column from a view in SQL?

What is difference between cursor and pointer?

The difference between the mouse pointer and cursor is as follows: The mouse pointer is an arrow-like figure that appears on the screen of the computer. It is used to locate the different icons on the screen. … The cursor, however, is a blinking line that appears whenever you type something on the computer.

What is cursor in SQL and its types?

Cursor is a Temporary Memory or Temporary Work Station. It is Allocated by Database Server at the Time of Performing DML(Data Manipulation Language) operations on Table by User. Cursors are used to store Database Tables. There are 2 types of Cursors: Implicit Cursors, and Explicit Cursors.

Categories BD