SQL Query to Update All Rows in a Table

Updating all rows in a SQL table is a common task when we need to make changes to every record without specifying individual rows. This operation can be performed using the UPDATE statement combined with the SET clause, which allows for modifying values across all rows of a specified table. Understanding this process is crucial for database management and data manipulation, making it a fundamental skill for both beginners and advanced SQL users.

In this article, we will walk us through the process of updating all rows in a SQL table using the UPDATE statement. We will cover the necessary syntax, provide step-by-step instructions, and offer practical examples to help us understand how to efficiently modify data across all records in a table.

Step-by-Step Guide to Update All Rows in a SQL Table

This guide provides a detailed step-by-step process to update all rows in a SQL table using the UPDATE statement. Learn how to apply changes across every row in a table with practical examples to enhance your SQL skills.

Step 1: CREATE DATABASE

To begin, we need to create a new SQL database where your table will reside. This can be done using the CREATE DATABASE statement. The database serves as a container for our tables, allowing for better organization and management of your data.

Query:

CREATE DATABASE database_name;

Step 2: Create a Table

Next, we will create a table to store your data. For this example, let’s say we need a table named products with three columns: product_id, product_name, and product_cost. The product_id column is defined as a primary key to uniquely identify each product.

Query:

CREATE TABLE products(product_id int 
primary key, product_name varchar(45),
 product_cost float);

Step 3: Insert Sample Data into the Table

After creating the table, we can populate it with sample data using the INSERT INTO statement. This data will be used for demonstration purposes in subsequent steps.

Query: 

INSERT INTO products VALUES
(1001,'Colgate Toothpaste', 2.25),
(1002, 'Sensodyne Toothpaste', 2.30),
(1003, 'Listrine Mouthwash', 1.75), 
(1004, 'T-Shirt', 1.75),
(1005, 'Pants', 2.35);

Step 4: Verify Data in the Table

To check that the data has been inserted correctly, we can use the SELECT * statement to display all rows in the products table.

Query:

SELECT * FROM products;

Output

Step 5: Update All Rows in the Table

To update all rows in the products table with a new value, use the UPDATE statement followed by the SET clause. Since no WHERE condition is specified, the change will affect every row in the table. This is useful when we need to modify a field universally across the entire dataset.

Syntax

UPDATE table_name SET column_name1 = new_value1,
column_name2 = new_value2 —- ;

Here table_name is the name of the table, column_name is the column whose value we want to update, new_value is the updated value. Let’s look at an example. Now our task is to update the product_cost to 4,  for all product_id(s), so let’s see how it is done.

Query:

UPDATE products SET product_cost = 4;

Output

Explanation:

After executing this query, the product_cost for every product in the products table will be updated to 4. This operation does not require conditions as it affects all rows.

Step 6: Update Rows with Conditions

If you only need to update specific rows based on a condition, you can include the WHERE clause in your UPDATE statement. For instance, if we want to change the product_cost for a specific product_id, you can specify it in the WHERE clause.

Syntax

UPDATE table_name SET column_name1 = new_value1,
column_name2 = new_value2 —- WHERE condition;

Here table_name is the name of the table, column_name is the column whose value you want to update, new_value is the updated value, WHERE is used to filter for specific data. Now our task is to update the product_cost to 4,  for product_id 1001, so let’s see how it is done.

Query:

UPDATE products SET product_cost 
= 4 WHERE product_id = 1001;

Output

Conclusion

Updating all rows in a SQL table is a straightforward and powerful operation that ensures uniformity in data across all records. By using the UPDATE statement in combination with the SET and WHERE clauses, we can efficiently modify data as needed. Remember, SQL is case insensitive, but it is best practice to use uppercase for keywords (UPDATE, SET, WHERE) and lowercase for table and column names to maintain readability and consistency.