Cursor Example SQL Server

Hello, Dev! In this journal article, we will be discussing cursor examples in SQL Server. A cursor is a database object that allows you to retrieve and manipulate rows from a result set one at a time. Cursors are often used when you need to perform operations on each row of a result set individually. With that said, let’s dive into the topic!

What is a Cursor in SQL Server?

A cursor in SQL Server is a database object that allows you to iterate through a result set one row at a time. It is used in situations where you need to perform operations on each row individually. Cursors can be created using T-SQL code or through the SQL Server Management Studio. There are different types of cursors, and we will be discussing each of them in detail.

Types of Cursors in SQL Server

There are three types of cursors in SQL Server:

Type of Cursor	Description
Static Cursor	Retains a snapshot of the result set
Dynamic Cursor	Reflects all changes made to the rows in the result set
Forward-only Cursor	Only allows you to move forward through the result set

Let’s take a closer look at each of these cursors.

Static Cursor

A static cursor in SQL Server retains a snapshot of the result set. This means that if any changes are made to the rows in the result set, the cursor will not reflect those changes. This type of cursor is the least resource-intensive, but it also has the least functionality. Static cursors can only move forward through the result set.

To create a static cursor, you can use the following T-SQL code:

Dynamic Cursor

A dynamic cursor in SQL Server reflects all changes made to the rows in the result set. This means that if any changes are made to the rows, the cursor will also reflect those changes. Dynamic cursors can be used to move both forward and backward through the result set, and they provide more functionality than static cursors. However, dynamic cursors are more resource-intensive than static cursors.

To create a dynamic cursor, you can use the following T-SQL code:

Forward-only Cursor

A forward-only cursor in SQL Server only allows you to move forward through the result set. This type of cursor is the fastest and least resource-intensive, but it also has the least functionality. Forward-only cursors cannot move backward through the result set, and they do not support scrolling.

To create a forward-only cursor, you can use the following T-SQL code:

Example Scenarios Using Cursors

Now that we have discussed the different types of cursors in SQL Server, let’s look at some example scenarios where cursors can be useful.

Scenario 1: Updating a Column in a Table

Let’s say you have a table called “Employees”, and you need to update the “Salary” column for each employee. You can use a cursor to iterate through each row in the “Employees” table and update the “Salary” column for each employee.

Step 1: Create the Cursor

To create a cursor for this scenario, you can use the following T-SQL code:

Step 2: Iterate Through Rows and Update Column

Once you have created the cursor, you can use it to iterate through each row in the “Employees” table and update the “Salary” column for each employee. You can use the following T-SQL code to do this:

Scenario 2: Deleting Rows from a Table

Let’s say you have a table called “Orders”, and you need to delete all orders that have a status of “Cancelled”. You can use a cursor to iterate through each row in the “Orders” table and delete any rows where the “Status” column is equal to “Cancelled”.

Step 1: Create the Cursor

To create a cursor for this scenario, you can use the following T-SQL code:

Step 2: Iterate Through Rows and Delete Rows

Once you have created the cursor, you can use it to iterate through each row in the “Orders” table and delete any rows where the “Status” column is equal to “Cancelled”. You can use the following T-SQL code to do this:

FAQs

What is the Difference Between a Cursor and a While Loop?

A cursor in SQL Server is a database object that allows you to iterate through a result set one row at a time. A while loop, on the other hand, is a programming construct that allows you to repeat a block of code while a condition is true. While loops can be used to iterate through a result set, but they are not as efficient as cursors.

When Should I Use a Cursor in SQL Server?

Cursors in SQL Server should be used sparingly, as they can be resource-intensive and slow down your queries. Cursors can be useful in situations where you need to perform operations on each row of a result set individually. However, before using a cursor, consider using other SQL Server features, such as set-based operations, to achieve the same result.

Can Cursors Be Nested?

Yes, cursors in SQL Server can be nested. This means that you can create a cursor within another cursor. However, it is important to use cursors judiciously, as nesting them can make your queries more complex and resource-intensive.

Conclusion

That wraps up our discussion on cursor examples in SQL Server, Dev! We hope you found this article informative and useful in your future SQL Server projects. Remember to use cursors judiciously, and consider using other SQL Server features, such as set-based operations, to achieve the same result. Happy querying!