Why cursor is used in SQL?


Why cursor is used in SQL?

The major function of a cursor is to retrieve data, one row at a time, from a result set, unlike the SQL commands which operate on all the rows in the result set at one time. Cursors are used when the user needs to update records in a singleton fashion or in a row by row manner, in a database table.

What is cursor in SQL with example?

Cursor is a database object to retrieve data from a result set one row at a time, instead of the T-SQL commands that operate on all the rows in the result set at one time. We use a cursor when we need to update records in a database table in singleton fashion means row by row.

What is cursor in MS SQL?

A SQL cursor is a database object that retrieves data from result sets one row at a time. The cursor in SQL can be used when the data needs to be updated row by row. A SQL cursor is a database object that is used to retrieve data from a result set one row at a time.

How does cursor work in SQL?

To use cursors in SQL procedures, you need to do the following:

  1. Declare a cursor that defines a result set.
  2. Open the cursor to establish the result set.
  3. Fetch the data into local variables as needed from the cursor, one row at a time.
  4. Close the cursor when done.

How do I run a cursor?

To open a cursor, you use the following syntax: OPEN cursor_name; In this syntax, the cursor_name is the name of the cursor declared in the declaration section. When you open a cursor, Oracle parses the query, binds variables, and executes the associated SQL statement.

What is cursor and its types?

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

Why is a cursor called a cursor?

Origin of the term Cursor is Latin for 'runner. ' A cursor is the name given to the transparent slide engraved with a hairline that is used for marking a point on a slide rule. The term was then transferred to computers through analogy.

How do I pass one cursor to another cursor?

1 Answer. It is possible to reference another cursor within the first one: declare cursor c1 is select distinct Assigned from table_name; cursor c2(p_Assigned in varchar2) is select id, Assigned from table_name where Assigned = p_Assigned; begin for r1 in c1 loop dbms_output.

Can we declare a cursor inside begin?

You can declare multiple cursors in the same pl/sql block. There is no need to declare the second cursor after you've opened the first cursor! ... Any time you see a nested cursor loop, you should IMMEDIATELY stop and look to see if you can combine the queries into a single select statement.

Can we open a cursor twice?

2 Answers. You need to open the cursor twice. Using a string variable to hold the query will prevent you from writing the query twice.

Can we use two cursors in a procedure?

Standard cursor in MySQL allow only one HANDLER. However, when we use multiple cursors like a nested loop, the handler will stop both cursors at the same time. Since we cannot declare two handlers for each cursor, we need to use BLOCK. Below is the example of MySQL's stored procedure using multiple cursors.

How do I store multiple values in a cursor?

Cursor Based Record Datatype With Cursor Returning Multiple Values In Oracle Database

  1. Step 1: Declare a Simple Explicit Cursor. A Cursor-based record datatype requires an already created cursor. ...
  2. Step2: Declare the Cursor Based Record Datatype Variable. ...
  3. Step 3: Initialize the Cursor-Record Variable.

How do I use multiple cursors in SQL Server?

There are generally very few times where a loop/cursor approach can't be replaced by a set-based approach. You can have the cursors nested but you need to declare/open/fetch/close/deallocate the inner cursor within the WHILE loop of the outer cursor.

Can we have two cursors in a procedure Oracle?

The trick to declaring a cursor within a cursor is that you need to continue to open and close the second cursor each time a new record is retrieved from the first cursor. That way, the second cursor will use the new variable values from the first cursor.

What is parameterized cursor in PL SQL?

Parameterized cursors are static cursors that can accept passed-in parameter values when they are opened. The cursor displays the name and salary of each employee in the EMP table whose salary is less than that specified by a passed-in parameter value. ...

How do you declare a cursor inside a for loop in Oracle?

DECLARE CURSOR IS ; BEGIN FOR I IN LOOP . ....FOR Loop Cursor statement

  1. In the above syntax, the declaration part contains the declaration of the cursor.
  2. The cursor is created for the 'SELECT' statement that is given in the cursor declaration.

What can a cursor FOR loop use?

The cursor FOR LOOP statement implicitly declares its loop index as a record variable of the row type that a specified cursor returns, and then opens a cursor. With each iteration, the cursor FOR LOOP statement fetches a row from the result set into the record.

How do I create a cursor in SQL?

Explanation of Cursor Syntax in SQL Server

  1. DECLARE statements - Declare variables used in the code block.
  2. SET\SELECT statements - Initialize the variables to a specific value.
  3. DECLARE CURSOR statement - Populate the cursor with values that will be evaluated. ...
  4. OPEN statement - Open the cursor to begin data processing.

What is cursor status?

For a given parameter, CURSOR_STATUS shows whether or not a cursor declaration has returned a cursor and result set. Transact-SQL Syntax Conventions.

What is Cursor option?

1) A cursor is the position indicator on a computer display screen where a user can enter text. In an operating system with a graphical user interface (GUI), the cursor is also a visible and moving pointer that the user controls with a mouse, touch pad, or similar input device.

What is Logo cursor called?

Explanation: The mouse cursor is called a pointer in logo, owing to its resemblance in usage to a pointing stick.

What is the hand cursor called?

It is also called a pointer, but today pointer refer to a specific cursor, the one that looks like a hand with an extended index finger.

How do you customize your cursor?

Q: How to use Custom Cursor?

  1. Custom Cursor menu. To activate Custom Cursor extension click on its icon located at Chrome toolbar. ...
  2. Setting the cursor. Go to Custom Cursor pop-up window, scroll down and choose the desired cursor pack and click on it. ...
  3. Changing the size. ...
  4. Disabling Custom Cursor.

Why isn't my custom cursor showing up?

Press Windows key + X. Click on Control Panel, click Mouse. On the displayed Mouse Properties box, go to Pointer Options tab. On the selected tab, uncheck Hide pointer while typing checkbox under Visibility section.

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