Understanding Update Statement in SQL Server

Dear Dev, if you are reading this article, then you are probably someone who is interested in SQL Server and its functionalities. SQL Server is an immensely popular database management system that has been around for almost three decades now. Its functionalities are immense, and it is widely used in various industries. In this article, we will be discussing one of the important functionalities of SQL Server, i.e., the Update Statement.

What is an Update Statement?

In SQL Server, the Update Statement is used to modify the values of one or more columns in an existing table. It allows you to change the data that is stored in a table. The Update Statement is used to change the existing data in one or more rows in a table. You can use it to update a single row, multiple rows, or all the rows in a table.

Let’s take an example to understand how an Update Statement works:

EmpID	EmpName	EmpSalary
1001	John	$5000
1002	Jane	$7000
1003	Mark	$6000

Suppose you want to update the salary of Jane to $8000. You can use the following Update Statement:

UPDATE Employee SET EmpSalary='$8000' WHERE EmpName='Jane'

This statement will update the salary of Jane to $8000 in the Employee table.

Syntax of Update Statement

The syntax of the Update Statement is as follows:

UPDATE table_name SET column1=value1, column2=value2,...WHERE some_column=some_value

The Update Statement consists of three parts:

• Table Name: The name of the table that you want to update.
• SET: The keyword that is used to specify the columns that you want to update and their new values.
• WHERE: The keyword that is used to specify the condition that must be met to update the rows.

Let’s understand each part in detail.

Table Name

The Table Name is the name of the table that you want to update. It must be specified after the UPDATE keyword. For example:

UPDATE Employee SET EmpSalary='$8000'

This statement will update the EmpSalary column in the Employee table.

SET

The SET keyword is used to specify the columns that you want to update and their new values. You can update one or more columns at the same time. For example:

UPDATE Employee SET EmpSalary='$8000', EmpDesignation='Manager'

This statement will update the EmpSalary and EmpDesignation columns in the Employee table.

WHERE

The WHERE keyword is used to specify the condition that must be met to update the rows. It is used to filter the rows that you want to update. For example:

UPDATE Employee SET EmpSalary='$8000' WHERE EmpName='Jane'

This statement will update the EmpSalary column for the row where EmpName is Jane.

FAQ

1. Can I update multiple rows using a single Update Statement?

Yes, you can update multiple rows using a single Update Statement. You just need to specify the conditions that must be met to update the rows. For example:

UPDATE Employee SET EmpSalary='$8000' WHERE EmpDesignation='Manager'

This statement will update the EmpSalary column for all the rows where EmpDesignation is Manager.

2. What is the difference between Update Statement and Insert Statement?

The Update Statement is used to modify the existing data in a table, whereas the Insert Statement is used to add new data to a table. The Update Statement only modifies the existing rows, whereas the Insert Statement adds new rows to the table.

3. Can I use the Update Statement to modify multiple columns at once?

Yes, you can use the Update Statement to modify multiple columns at once. You just need to specify the new values for each column that you want to modify. For example:

UPDATE Employee SET EmpSalary='$8000', EmpDesignation='Manager' WHERE EmpName='Jane'

This statement will update the EmpSalary and EmpDesignation columns for the row where EmpName is Jane.

4. What happens if I don’t specify a WHERE clause in the Update Statement?

If you don’t specify a WHERE clause in the Update Statement, then all the rows in the table will be updated with the new values that you have specified. This can be dangerous and can cause data loss if not done carefully.

5. Can I use the Update Statement to modify data in multiple tables at once?

No, you cannot use the Update Statement to modify data in multiple tables at once. You need to use the Join Statement to join the tables and then update the data.

That’s all for this article. We hope you found it informative and helpful. Keep learning!