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Mastering SQL Server UPDATE JOIN Statement for Efficient Multi-Table Updates

The SQL Server UPDATE JOIN Statement – A Comprehensive Guide

When it comes to updating data in a SQL Server database, the UPDATE statement is the primary tool for modifying existing data. But what happens when the data that needs to be updated is spread across multiple tables?

In such cases, the SQL Server UPDATE JOIN statement comes into play.

In this article, we will explore how to use the UPDATE JOIN statement to perform cross-table updates in SQL Server with the help of practical examples.

SQL Server UPDATE JOIN Syntax

Firstly, let’s take a look at the UPDATE JOIN statement syntax:

“`

UPDATE table1

JOIN table2

ON table1.column = table2.column

SET table1.column = ‘value’, table2.column = ‘value’;

“`

In the above syntax, we can see that we are performing an UPDATE statement on `table1` and joining it with `table2` using the `JOIN` clause. We can specify the join type as `INNER`, `LEFT`, `RIGHT`, or `FULL OUTER` join, as per our requirements.

The `ON` clause specifies the join condition between the two tables. Here, we are joining `table1` and `table2` based on a common column named `column`.

Finally, the SET clause specifies the columns that need to be updated for both tables.

SQL Server UPDATE JOIN Examples

To demonstrate how the UPDATE JOIN statement is used in practice, let’s consider two sample tables: `sales.targets` and `sales.commissions`. Creating the `sales.targets` Table

“`

CREATE TABLE sales.targets (

id INT NOT NULL PRIMARY KEY,

month VARCHAR(10) NOT NULL,

year INT NOT NULL,

target_amt DECIMAL(10,2) NOT NULL

);

INSERT INTO sales.targets VALUES

(1, ‘Jan’, 2021, 100000.00),

(2, ‘Feb’, 2021, 90000.00),

(3, ‘Mar’, 2021, 110000.00),

(4, ‘Apr’, 2021, 95000.00),

(5, ‘May’, 2021, 105000.00),

(6, ‘Jun’, 2021, 85000.00);

“`

Creating the `sales.commissions` Table

“`

CREATE TABLE sales.commissions (

id INT NOT NULL PRIMARY KEY,

sale_amt DECIMAL(10,2) NOT NULL,

commission DECIMAL(10,2),

month VARCHAR(10) NOT NULL,

year INT NOT NULL

);

INSERT INTO sales.commissions VALUES

(1, 120000.00, NULL, ‘Jan’, 2021),

(2, 80000.00, NULL, ‘Feb’, 2021),

(3, 130000.00, NULL, ‘Mar’, 2021),

(4, 100000.00, NULL, ‘Apr’, 2021),

(5, 90000.00, NULL, ‘May’, 2021),

(6, 75000.00, NULL, ‘Jun’, 2021);

“`

Now that we have our sample tables set up, let’s look at some practical examples of how to use the UPDATE JOIN statement.

Example 1: Updating Commissions based on Sales Targets

Suppose we have a requirement to update the `commission` column of the `sales.commissions` table based on the given sales targets. We can achieve this using an INNER JOIN between `sales.commissions` and `sales.targets`.

“`

UPDATE sales.commissions

INNER JOIN sales.targets

ON sales.commissions.month = sales.targets.month

AND sales.commissions.year = sales.targets.year

SET sales.commissions.commission =

CASE

WHEN sales.commissions.sale_amt >= sales.targets.target_amt * 1.25

THEN sales.commissions.sale_amt * 0.15

WHEN sales.commissions.sale_amt >= sales.targets.target_amt * 1.1

THEN sales.commissions.sale_amt * 0.1

ELSE sales.commissions.sale_amt * 0.05

END;

“`

In the above example, we are updating the `sales.commissions` table based on the sales target data from the `sales.targets` table. We can see that we are using an INNER JOIN between the two tables based on the month and year columns.

The `SET` clause specifies that we need to update the `commission` column of the `sales.commissions` table based on a specific calculation. Here, we are using a `CASE` statement to determine the commission rate based on the achieved sales target.

Example 2: Updating Sales Targets for a Specific Month

Let’s consider another example, where we need to update the sales target data for a specific month. We can achieve this using a LEFT JOIN between `sales.targets` and a temporary table with the desired values.

“`

UPDATE sales.targets

LEFT JOIN (

SELECT ‘Jun’ AS month, 2021 AS year, 90000.00 AS target

) AS temp

ON sales.targets.month = temp.month

AND sales.targets.year = temp.year

SET sales.targets.target_amt = temp.target

WHERE sales.targets.month = ‘Jun’ AND sales.targets.year = 2021;

“`

In the above example, we are updating the `sales.targets` table for the month of June, 2021. We can see that we are using a LEFT JOIN between `sales.targets` and a temporary table with the desired target value.

The `SET` clause specifies that we need to update the sales target data for the given month and year. The `WHERE` clause is used as an additional filter to ensure that we only update the specific month and year records.

Conclusion

The SQL Server UPDATE JOIN statement is a powerful tool for performing cross-table updates. With the examples provided in this article, we hope that you now have a deeper understanding of how to use the UPDATE JOIN statement in practical scenarios.

By using the right JOIN type and specifying the correct conditions, we can update data across multiple tables with ease.

3) SQL Server UPDATE INNER JOIN Example

The SQL Server INNER JOIN combines rows from two or more tables based on a related column between them. When it comes to updating data using the INNER JOIN, we can update multiple columns in one or more tables simultaneously.

One practical example of using the UPDATE INNER JOIN statement is to calculate commissions for sales staff.

Lets say we have two tables: `sales` and `commissions`, where the `sales` table contains the sales data, and `commissions` table contains the sales commission data for sales staff.

We want to join these tables and calculate commissions using a formula.

Creating the `sales` Table

“`

CREATE TABLE sales (

id INT NOT NULL PRIMARY KEY,

salesperson VARCHAR(100) NOT NULL,

sale_amt DECIMAL(10,2) NOT NULL,

sale_date DATE NOT NULL

);

INSERT INTO sales VALUES

(1, ‘John Doe’, 1500.00, ‘2021-09-14’),

(2, ‘Jane Doe’, 3500.00, ‘2021-09-15’),

(3, ‘Bob Smith’, 2000.00, ‘2021-09-15’),

(4, ‘Mary Johnson’, 1000.00, ‘2021-09-16’);

“`

Creating the `commissions` Table

“`

CREATE TABLE commissions (

id INT NOT NULL PRIMARY KEY,

salesperson VARCHAR(100) NOT NULL,

commission DECIMAL(10,2)

);

“`

Now, let’s assume that the sales commission is calculated based on a fixed percentage of the sale amount. In our case, the commission rate is 10%.

So, we need to calculate the commission amount for each sale and update the `commissions` table accordingly.

We can achieve this using an UPDATE INNER JOIN statement.

“`

UPDATE commissions

INNER JOIN sales ON commissions.salesperson = sales.salesperson

SET commissions.commission = sales.sale_amt * 0.1;

“`

In the above example, we have used an INNER JOIN to join the `commissions` table with the `sales` table. We have matched the `salesperson` column of both tables to link the sales data to the appropriate salesperson in the `commissions` table.

The `SET` clause specifies that we need to update the `commission` column of the `commissions` table using a calculation. As we need to calculate sales commission as 10% of the `sale_amt` column from the `sales` table, we have multiplied the `sale_amt` column by 0.1 (which represents the 10% rate) to calculate the commission amount.

4) SQL Server UPDATE LEFT JOIN Example

The SQL Server LEFT JOIN returns all the rows from the left table and matching rows from the right table. When used along with the UPDATE statement, we can update data in the left table and insert nulls in columns where corresponding data is not found in the right table.

One practical example of using the UPDATE LEFT JOIN statement is to update new sales staff commissions.

Lets say we have two tables: `staff` and `commissions`, where the `staff` table contains the sales staff data, and `commissions` table contains the sales commission data for all sales staff.

We want to update the `commissions` table with the commissions for new sales staff.

Creating the `staff` Table:

“`

CREATE TABLE staff (

id INT NOT NULL PRIMARY KEY,

name VARCHAR(100) NOT NULL

);

INSERT INTO staff VALUES

(1, ‘John Doe’),

(2, ‘Jane Doe’),

(3, ‘Bob Smith’),

(4, ‘Mary Johnson’),

(5, ‘Emily Brown’),

(6, ‘Tom Allen’);

“`

Creating the `commissions` Table:

“`

CREATE TABLE commissions (

id INT NOT NULL PRIMARY KEY,

name VARCHAR(100) NOT NULL,

commission DECIMAL(10,2)

);

INSERT INTO commissions VALUES

(1, ‘John Doe’, 2350.00),

(2, ‘Jane Doe’, 4750.00),

(3, ‘Bob Smith’, 2760.00),

(4, ‘Mary Johnson’, 1230.00);

“`

Now let’s say we need to update the `commissions` table to add commission data for our two new sales staff members, Emily Brown and Tom Allen.

We can achieve this using an UPDATE LEFT JOIN statement.

“`

UPDATE commissions

LEFT JOIN (SELECT id, name FROM staff) AS s ON commissions.name = s.name

SET commissions.commission = COALESCE(commissions.commission, 0);

“`

In the above example, we have used a LEFT JOIN to join the `commissions` table with a temporary table created from the `staff` table. We have used the `COALESCE` function to avoid updating a null value in the `commission` column.

The `SET` clause specifies that we need to update the `commission` column of the `commissions` table by setting the default value of 0 if the value is null.

As we are doing a LEFT JOIN, it means that if the `name` in the `commissions` table does not match any `name` in the `staff` table, then that particular row from the `commissions` table will be updated with the default value of 0 in the `commission` column.

Conclusion

The SQL Server UPDATE statement is a powerful tool that can update data across multiple tables as per our requirements. By using the appropriate JOIN type, we can join the tables based on matching columns and update the columns that need modification.

We have provided practical examples of using the UPDATE INNER JOIN statement to calculate sales commissions and the UPDATE LEFT JOIN statement to update new sales staff commissions. With these examples, you can now update data efficiently in your SQL Server databases.

In conclusion, the SQL Server UPDATE JOIN statement is an essential tool for updating data in multiple tables simultaneously. By using the appropriate JOIN type, we can join the tables based on matching columns and update the columns that need modification.

The examples provided in this article demonstrate how to use this statement, including the UPDATE INNER JOIN to calculate sales commissions and the UPDATE LEFT JOIN to update new sales staff commissions. These practical examples highlight the significance of this topic for database management and provide useful takeaways for database developers and administrators.

With these tools and concepts in mind, developers and administrators can effectively update data in their SQL Server databases, saving time and resources.

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