EDUCBA

EDUCBA

MENUMENU
  • Free Tutorials
  • Free Courses
  • Certification Courses
  • 600+ Courses All in One Bundle
  • Login
Home Data Science Data Science Tutorials SQL Tutorial Cursors in SQL
Secondary Sidebar
SQL Tutorial
  • Advanced
    • MDF File in SQL Server
    • SQL Aliases
    • SQL Hosting
    • SQL Auto Increment
    • SQL Injection
    • SQL Wildcards
    • SQL Check
    • SQL Indexes
    • Select Distinct
    • SQL BETWEEN
    • SQLPlus spool
    • SQL Create Table
    • SQL Schema
    • Comparison Operators in SQL
    • SQL_plus
    • SQL Formatter
    • SQL LEFT INNER JOIN
    • SQL Plus Command
    • SQLPlus not found
    • SQL Injection Attack
    • Aggregate Functions in SQL
    • SQL REVOKE
    • SQL Select Distinct Count
    • IF ELSE Statement in SQL
    • SQL CASE Statement
    • SQL While Loop
    • SQL BIGINT
    • SQL Crosstab
    • SQL Wildcard Character
    • SQL INSTR()
    • SQL now
    • SQL synonyms
    • SQLite?export to csv
    • What is Procedure in SQL
    • Stored Procedure in SQL?
    • SQL Server Constraints
    • SQL DELETE ROW
    • Column in SQL
    • Table in SQL
    • SQL Virtual Table
    • SQL Merge Two Tables
    • SQL Table Partitioning
    • SQL Temporary Table
    • SQL Clone Table
    • SQL Rename Table
    • SQL LOCK TABLE
    • SQL Clear Table
    • SQL DESCRIBE TABLE
    • SQL Mapping
    • Cursors in SQL
    • AND in SQL
    • Wildcard in SQL
    • SQL FETCH NEXT
    • SQL Views
    • SQL Delete View
    • Triggers in SQL
    • SQL UPDATE Trigger
    • SQL AFTER UPDATE Trigger
    • SQL Update Statement
    • SQL DROP TRIGGER
    • SQL DROP Table
    • Types of SQL Views
    • SQL Port
    • SQL Clustered Index
    • SQL COMMIT
    • Distinct Keyword in SQL
    • PARTITION BY in SQL
    • SQL Set Operators
    • SQL UNION ALL
    • Metadata in SQL
    • SQL Bulk Insert
    • Array in SQL
    • SQL REGEXP
    • JSON in SQL
    • SQL For loop
    • EXPLAIN in SQL
    • ROLLUP in SQL
    • Escape Character SQL
    • SQL Cluster
    • SQL Backup
    • SQL Pattern Matching
    • SQL Users
    • ISNULL SQL Server
    • SQL pivot
    • SQL Import CSV
    • SQL if then else
    • SQL ignore-case
    • SQL Matches
    • SQL Search String
    • SQL Column Alias
    • SQL extensions
    • SQL Substring Function
    • Charindex SQL
  • Basic
    • What is SQL
    • Careers in SQL
    • Careers in SQL Server
    • IS SQL Microsoft?
    • SQL Management Tools
    • What is SQL Developer
    • Uses of SQL
    • How to Install SQL Server
    • What is SQL Server
    • SQL Quick References
    • SQL Like Wildcard
    • SQL Like with Multiple Values
    • SQL Examples
    • SQL Server Versions
    • SQL DROP DB
    • SQL Case Insensitive
    • SQL Expressions
    • Database in SQL
    • SQL Data Types
    • SQL Keywords
    • Composite Key in SQL
    • SQL WAITFOR
    • SQL Constraints
    • Transactions in SQL
    • First Normal Form
    • SQL Server Data Types
    • SQL Administration
    • SQL Variables
    • SQL Enum
    • SQL GROUP BY WHERE
    • SQL ROW
    • SQL EXECUTE
    • SQL EXCLUDE
    • SQL Performance Tuning
    • SQL UUID
    • Begin SQL
    • SQL Update Join
    • Cheat sheet SQL
  • Operators
    • SQL Operators
    • SQL Arithmetic Operators
    • SQL Logical Operators
    • SQL String Operators
    • Ternary Operator in SQL
  • Commands
    • SQL Commands
    • sqlplus set commands
    • SQL Alter Command
    • SQL Commands Update
    • SQL DML Commands
    • SQL DDL Commands
    • FETCH in SQL
  • Clause
    • SQL Clauses
    • SQL IN Operator
    • SQL SELECT DISTINCT Multiple Columns
    • SQL Null Values
    • SQL LIKE
    • SQL LIKE Query
    • SQL LIKE Operator
    • SQL LIKE Clause
    • SQL NOT Operator
    • SQL Minus
    • SQL WHERE Clause
    • SQL with Clause
    • SQL HAVING Clause
    • SQL HAVING Clause
    • SQL GROUP BY DAY
    • ORDER BY Clause in SQL
    • SQL ORDER BY CASE
    • SQL ORDER BY DESC
    • SQL ORDER BY DATE
    • SQL ORDER BY Alphabetical
    • SQL ORDER BY Ascending
    • SQL Order by Count
    • SQL GROUP BY Month
    • SQL GROUP BY Multiple Columns
    • SQL GROUPING SETS
  • Queries
    • SQL Insert Query
    • SQL SELECT Query
    • SQL SELECT RANDOM
    • SQL Except Select
    • SQL Subquery
    • SQL SELECT DISTINCT
    • SQL WITH AS Statement
  • Keys
    • SQL Keys
    • SQL Foreign Key
    • Primary Key in SQL
    • Foreign Key in SQL
    • Unique Key in SQL
    • SQL UNIQUE Constraint
    • SQL Primary Key
    • Alternate Key in SQL
    • SQL Super Key
  • Functions
    • SQL Date Function
    • SQL Server Functions
    • SQL String Functions
    • SQL Compare String
    • Timestamp to Date in SQL
    • SQL REGEX
    • SQL Window Functions
    • SQL Syntax
    • SQL CONCAT
    • SQL ALTER TABLE
    • SQL MOD()
    • SQL Timestamp
    • SQL Min and Max
    • SQL TO_DATE()
    • SQL DATEADD()
    • SQL DATEDIFF()
    • SQL HOUR()
    • SQLite? functions
    • ANY in SQL
    • LIKE Query in SQL
    • SQL NOT NULL
    • SQL NOT IN
    • SQL MAX()
    • SQL MIN()
    • SQL SUM()
    • SQL COUNT
    • SQL identity
    • SQL DELETE Trigger
    • SQL Declare Variable
    • SQL Text Search
    • SQL COUNT DISTINCT
    • SQL TEXT
    • SQL Limit Order By
    • BETWEEN in SQL
    • LTRIM() in SQL
    • TOP in SQL
    • SQL Select Top
    • Merge SQL
    • SQL TRUNCATE()
    • SQL UNION
    • SQL ALL
    • SQL INTERSECT
    • SQL Alias
    • SQL Server Substring
    • CUBE in SQL
    • SQL RANK()
    • SQL CTE
    • SQL LAG()
    • SQL MID
    • SQL avg()
    • SQL WEEK
    • SQL DELETE
    • SQL DATEPART()
    • SQL DECODE()
    • SQL DENSE_RANK()
    • SQL NTILE()
    • SQL NULLIF()
    • SQL Stuff
    • SQL Ceiling
    • SQL EXISTS
    • SQL LEAD()
    • SQL COALESCE
    • SQL BLOB
    • SQL ROW_NUMBER
    • SQL Server Replace
    • SQL Ranking Function
    • SQL Server Permission
  • T-SQL
    • T-SQL pivot
    • T-SQL Formatter
    • T-SQL TRY CATCH
    • T-SQL CTE
    • T-SQL CASE
    • T-SQL DATEPART
    • T-SQL Date Format
    • T-SQL ROUND
    • T-SQL Loop
    • T-SQL IIF
    • T-SQL Union
    • T-SQL CREATE TABLE
    • T-SQL INSERT
    • T-SQL Stuff
    • T-SQL ISNULL
    • T-SQL ADD Column
    • T-SQL DATEDIFF
  • Joins
    • Join Query in SQL
    • Types of Joins in SQL
    • Types of Joins in SQL Server
    • SQL Inner Join
    • SQL Join Two Tables
    • SQL Delete Join
    • SQL Left Join
    • LEFT OUTER JOIN in SQL
    • SQL Right Join
    • SQL Cross Join
    • SQL Outer Join
    • SQL Full Join
    • SQL Self Join
    • Natural Join SQL
    • SQL Multiple Join
  • SqlAlchemy
    • What is SQLAlchemy
    • SqlAlchemy ORM
    • SQLAlchemy count
    • SQLAlchemy update object
    • SQLAlchemy pip
    • SQLAlchemy Connection
    • SQLAlchemy Metadata
    • SQLAlchemy Raw SQL
    • SQLAlchemy Filter in List
    • SQLAlchemy Alias
    • SQLAlchemy unique
    • SQLAlchemy JSONB
    • SQLAlchemy Async
    • SQLAlchemy Types
    • SQLAlchemy Many to Many
    • SQLAlchemy Example
    • SQLAlchemy Model
    • SQLAlchemy Data Types
    • SQLAlchemy Filter
    • SQLAlchemy SQLite
    • SQLAlchemy DateTime
    • SQLAlchemy create_engine
    • SQLAlchemy Delete
    • SQLAlchemy Migrations
  • NoSQL
    • NoSQL Databases List
    • NoSQL Data Modeling
    • Types of NoSQL Databases
    • NoSQL Injection
    • NoSQL vs SQL Databases
    • NoSQL Use Cases
    • NoSQL Key Value
  • Interview Questions
    • SQL Interview Questions
    • Advance SQL Interview Questions
    • SQL Joins Interview Questions
    • SQL Server Interview Questions
    • SQL Current Month

Related Courses

JDBC Training Course

PHP course

Windows 10 Training

SQL Course Training

PL/SQL Certification Courses

Oracle Certification Courses

Cursors in SQL

By Priya PedamkarPriya Pedamkar

Cursors in SQL

Introduction to Cursors in SQL

A cursor in SQL is a momentary memory space formed in the computer memory whenever an SQL statement is run, where it is used to position the row that is currently being worked on. It is used to manage the records in a table by fetching data from the database after running a query in an order that trails one row at a time. This cursor can keep hold of an ‘active set’ for more than one record during a query execution but cannot keep actively processing more than one record.

So, cursors create a temporary workspace with the selected set of rows and a pointer that points to the current row. This set of rows, on which the cursor will perform the desired operation, is called an Active Data Set. The pointer retrieves the rows from the result set one by one. You can then perform any SQL operation one row at a time.

Implicit Cursors

Implicit cursors, as the name implies, are generated by the SQL parser for DML queries. DML queries are Data Manipulation Queries. These queries manipulate or change the data. They do not interfere with the structure or the schema of the database. Queries such as SELECT, INSERT, UPDATE, and DELETE generate an implicit cursor. Implicit cursors are hidden to the end-user.

Explicit Cursors

Explicit cursors are user-generated cursors. When a user instructs the SQL parser to create a cursor for an active set, the cursor thus created is called an explicit cursor. The active set is defined through a SELECT query by the user. We would be covering explicit cursors in detail in this article.

Start Your Free Software Development Course

Web development, programming languages, Software testing & others

Cursor Actions – The Lifecycle of a Cursor

The lifecycle of a cursor typically involves five stages:

Cursors in SQL 1

1. Declare: The first step is to declare a cursor. This step instructs the system to generate a cursor with the given data set. The data set is constructed using a SQL statement. At this stage, the active set is created, but the cursor’s temporary workspace is not yet opened in the memory.

2. Open: Next, the system is instructed to open the cursor. At this stage, the temporary workspace is loaded in the memory with the active set, and a pointer is generated, which points to the first row in the active set.

3. Fetch: This is the recurring step in the whole process. The pointer’s current row is fetched, and the desired task is performed on the row data. The pointer moves to the next row in the cursor.

4. Close: After the data manipulation is done, the cursor needs to be closed.

5. Deallocate: This is the final step to delete the cursor and release the memory, processor and other system resources allocated to the cursor.

Explicit Cursors – In Action!

Okay, so now we have a basic understanding of what cursors are and how they work. It’s time to get our hands dirty and create an explicit cursor ourselves.

Cursors in SQL Syntax

The Terminology of Cursors in SQL

Let’s understand the terminologies used in this syntax.

All in One Software Development Bundle(600+ Courses, 50+ projects)
Python TutorialC SharpJavaJavaScript
C Plus PlusSoftware TestingSQLKali Linux
Price
View Courses
600+ Online Courses | 50+ projects | 3000+ Hours | Verifiable Certificates | Lifetime Access
4.6 (86,818 ratings)

Cursor Scope

  • Cursor Scope can be either GLOBAL or LOCAL. A global cursor is available throughout the connection. A local cursor is scope-limited only to the stored procedures, functions or the query that holds the cursor.
  • This is the MS SQL Server-specific feature. MySQL supports local scoped cursors only.

Cursor Movement

  • MS SQL Server also gives the option to set the Cursor movement. It can be either the conventional Forward_Only mode, which moves the pointer from the first row until the last line. Or, it can be scrolled to the first, last, previous or next row.
  • Cursors in MySQL are non-scrollable.

Cursor Type

  • A cursor can be static as in it can cache the active set till deallocation and can juggle forward and backward through this cached active set. A cursor can be fast_forward only in static mode.
  • It can also be dynamic to allow the addition or deletion of rows in the active set while the cursor is open. These changes are not visible to other users of the cursor in keyset mode. Cursors in MySQL are fast_forward only.

Cursor Lock

  • Cursor locks are useful in a multi-user environment. They lock the row so that no two users operate on the same data simultaneously. This ensures data integrity.
  • A read-only lock states that the row cannot be updated.
  • Scroll-locks lock the row as they are fetched in the cursor, ensuring that the task succeeds and updated data is available outside the cursor. Optimistic attempts to update the row without any lock. Thus, if the row has been updated outside the cursor, the task will not succeed.
  • MySQL supports only read-only locks. This means that MySQL won’t update the actual table; rather, it would copy the data to carry out update commands.

Thus, we see that these options are available only in MS SQL Server. This makes the syntax for MySQL cursors even more simple.

Example

Let us now update the salary of employees in our Employee table.

We would be using the below data in these cursors in SQL example.

Cursors in SQL 2

Our cursor code would be as follows:

DECLARE @sal float
DECLARE @newsal float
DECLARE Emp_Cur CURSOR FOR SELECT Salary, Updated_Salary FROM Employees
OPEN Emp_Cur
FETCH NEXT FROM Emp_Cur INTO @sal, @newsal
WHILE @@FETCH_STATUS = 0
BEGIN
SET @newsal = @sal*1.25
UPDATE Employees SET Updated_Salary = @newsal WHERE CURRENT OF Emp_Cur
FETCH NEXT FROM Emp_Cur INTO @sal, @newsal
END
CLOSE Emp_Cur
DEALLOCATE Emp_Cur

And the Output after executing the above cursor command would be:

Output

Conclusion – Cursors in SQL

Thus, we have seen what cursors are, how to use them and where to avoid them. Cursors do prove to be a helpful utility for developers but at the cost of performance. So, be careful when you opt for cursors.

Recommended Articles

This is a guide to Cursors in SQL. Here we discuss the types, lifecycle, and terminology of the cursor in SQL with examples. You can also go through our other suggested articles –

  1. SQL Views
  2. Cursors in PL/SQL
  3. Cursor in MySQL
  4. Cursors in PostgreSQL
Popular Course in this category
SQL Training Program (7 Courses, 8+ Projects)
  7 Online Courses |  8 Hands-on Projects |  73+ Hours |  Verifiable Certificate of Completion
4.5
Price

View Course

Related Courses

JDBC Training (6 Courses, 7+ Projects)4.9
PHP Training (5 Courses, 3 Project)4.8
Windows 10 Training (4 Courses, 4+ Projects)4.7
PL SQL Training (4 Courses, 2+ Projects)4.7
Oracle Training (14 Courses, 8+ Projects)4.7
0 Shares
Share
Tweet
Share
Primary Sidebar
Footer
About Us
  • Blog
  • Who is EDUCBA?
  • Sign Up
  • Live Classes
  • Corporate Training
  • Certificate from Top Institutions
  • Contact Us
  • Verifiable Certificate
  • Reviews
  • Terms and Conditions
  • Privacy Policy
  •  
Apps
  • iPhone & iPad
  • Android
Resources
  • Free Courses
  • Java Tutorials
  • Python Tutorials
  • All Tutorials
Certification Courses
  • All Courses
  • Software Development Course - All in One Bundle
  • Become a Python Developer
  • Java Course
  • Become a Selenium Automation Tester
  • Become an IoT Developer
  • ASP.NET Course
  • VB.NET Course
  • PHP Course

ISO 10004:2018 & ISO 9001:2015 Certified

© 2022 - EDUCBA. ALL RIGHTS RESERVED. THE CERTIFICATION NAMES ARE THE TRADEMARKS OF THEIR RESPECTIVE OWNERS.

EDUCBA
Free Software Development Course

C# Programming, Conditional Constructs, Loops, Arrays, OOPS Concept

*Please provide your correct email id. Login details for this Free course will be emailed to you

By signing up, you agree to our Terms of Use and Privacy Policy.

EDUCBA Login

Forgot Password?

By signing up, you agree to our Terms of Use and Privacy Policy.

EDUCBA
Free Software Development Course

Web development, programming languages, Software testing & others

*Please provide your correct email id. Login details for this Free course will be emailed to you

By signing up, you agree to our Terms of Use and Privacy Policy.

EDUCBA

*Please provide your correct email id. Login details for this Free course will be emailed to you

By signing up, you agree to our Terms of Use and Privacy Policy.

Let’s Get Started

By signing up, you agree to our Terms of Use and Privacy Policy.

This website or its third-party tools use cookies, which are necessary to its functioning and required to achieve the purposes illustrated in the cookie policy. By closing this banner, scrolling this page, clicking a link or continuing to browse otherwise, you agree to our Privacy Policy

Loading . . .
Quiz
Question:

Answer:

Quiz Result
Total QuestionsCorrect AnswersWrong AnswersPercentage

Explore 1000+ varieties of Mock tests View more