SQL's Update Command

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Ngày cập nhật gần nhất: 1/5/2026

In the previous article, Mytour introduced you to the INSERT command in SQL, which is used to add new data rows to a table. In this article, Mytour will further introduce you to the UPDATE command in SQL, helping you grasp its syntax and usage.

Unlike the INSERT command in SQL, the UPDATE command is used to modify existing rows in a table.

Syntax of the UPDATE Command in SQL

Modify table_name

Assign value1 to column_name1,

value2 to column_name2, and so on

[WHERE condition]

In which:

table_name: the table name that needs to be updated.

column_name1, column_name2 .. : the columns to be changed.

value1, value2 ... : are the new values.

Note: In the structure of the UPDATE command in SQL, the WHERE clause specifies the affected rows. If you don't add a WHERE clause, the values of the columns for all rows will be affected.

Example of UPDATE command in SQL

To update the position of employees, the SQL UPDATE query looks like this:

UPDATE employees

Assign 'Mysore' to position

WHERE id = 101;

To adjust the salary of all employees, the query takes the form:

UPDATE employees

Adjust salary to increase by 20%;

Above, Mytour just introduced you to the SQL UPDATE command. If you have any questions or need clarification, please feel free to leave your comments below the article. Don't forget to explore some articles on commands like CREATE, DELETE, JOINS command in SQL,... on Mytour.

Frequently Asked Questions

What is the main purpose of the SQL UPDATE command?

The SQL UPDATE command is primarily used to modify existing data in a table. It allows users to change specific column values for one or more rows based on specified conditions, ensuring that the correct data is updated efficiently.

How does the WHERE clause function in an SQL UPDATE command?

The WHERE clause in an SQL UPDATE command determines which rows will be affected by the update. If the WHERE clause is omitted, all rows in the table will be modified, which can lead to unintended changes in the dataset.

Can you provide an example of an SQL UPDATE command in practice?

Certainly! An example of an SQL UPDATE command is: UPDATE employees SET position = 'Mysore' WHERE id = 101. This command updates the position of the employee with ID 101 to 'Mysore'.

What should be considered when using the UPDATE command in SQL?

When using the UPDATE command in SQL, it is crucial to include the WHERE clause to avoid modifying all rows unintentionally. Always double-check the conditions specified to ensure accurate updates and maintain data integrity.

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