UPDATE JOIN

To update the data entered in a single database table using SQL, you can use the UPDATE statement. However, to update the data in multiple database tables, we need to use the UPDATE… JOIN clause.

For instance, if a student changes their primary phone number and wishes to update it in their organizational database, the information needs to be modified in multiple tables like student records, laboratory records, canteen passes etc. Using the JOIN clause, you can combine all these tables into one, and then using UPDATE statement, you can update the student data in them simultaneously.

The SQL UPDATE… JOIN Clause

The UPDATE statement only modifies the data in a single table and JOINS in SQL are used to fetch the combination of rows from multiple tables, with respect to a matching field.

If we want to update data in multiple tables, we can combine multiple tables into one using JOINS and then update them using UPDATE statement. This is also known as cross-table modification.

Syntax

Following is the basic syntax of the SQL UPDATE… JOIN statement −

UPDATEtable(s)JOIN table2 ON table1.join_column = table2.join_column
SET table1.column1 = table2.new_value1, 
table1.column2 = table2.new_value2;</pre>


Where, JOIN can be: Regular Join, Natural Join, Inner Join, Outer Join, Left Join, Right Join, Full Join etc.



Example



Assume we have created a table named CUSTOMERS, which contains the personal details of customers including their name, age, address and salary etc., using the following query −



CREATETABLE CUSTOMERS (
   ID INTNOTNULL,
   NAME VARCHAR(20)NOTNULL,
   AGE INTNOTNULL,
   ADDRESS CHAR(25),
   SALARY DECIMAL(18,2),PRIMARYKEY(ID));



Now, insert values into this table using the INSERT statement as follows −



INSERTINTO CUSTOMERS VALUES(1,'Ramesh',32,'Ahmedabad',2000.00),(2,'Khilan',25,'Delhi',1500.00),(3,'Kaushik',23,'Kota',2000.00),(4,'Chaitali',25,'Mumbai',6500.00),(5,'Hardik',27,'Bhopal',8500.00),(6,'Komal',22,'Hyderabad',4500.00),(7,'Muffy',24,'Indore',10000.00);



The table will be created as −



ID
NAME
AGE
ADDRESS
SALARY
1
Ramesh
32
Ahmedabad
2000.00
2
Khilan
25
Delhi
1500.00
3
Kaushik
23
Kota
2000.00
4
Chaitali
25
Mumbai
6500.00
5
Hardik
27
Bhopal
8500.00
6
Komal
22
Hyderabad
4500.00
7
Muffy
24
Indore
10000.00



Let us create another table ORDERS, containing the details of orders made and the date they are made on.



CREATETABLE ORDERS (
   OID INTNOTNULL,DATEVARCHAR(20)NOTNULL,
   CUSTOMER_ID INTNOTNULL,
   AMOUNT DECIMAL(18,2));



Using the INSERT statement, insert values into this table as follows −



INSERTINTO ORDERS VALUES(102,'2009-10-08 00:00:00',3,3000.00),(100,'2009-10-08 00:00:00',3,1500.00),(101,'2009-11-20 00:00:00',2,1560.00),(103,'2008-05-20 00:00:00',4,2060.00);



The table is displayed as follows −



OID
DATE
CUSTOMER_ID
AMOUNT
102
2009-10-08 00:00:00
3
3000.00
100
2009-10-08 00:00:00
3
1500.00
101
2009-11-20 00:00:00
2
1560.00
103
2008-05-20 00:00:00
4
2060.00



Following UPDATE... JOIN query increments the salary of customers by 1000 with respect to the inflation of their order amount by 500 −



UPDATE CUSTOMERS 
JOIN ORDERS 
ON CUSTOMERS.ID = ORDERS.CUSTOMER_ID 
SET CUSTOMERS.SALARY = CUSTOMERS.SALARY +1000, 
ORDERS.AMOUNT = ORDERS.AMOUNT +500;



Verification



We can verify whether the changes are reflected in a table by retrieving its contents using the SELECT statement as follows −



SELECT*FROM CUSTOMERS;



The updated CUSTOMERS table is displayed as follows −



ID
NAME
AGE
ADDRESS
SALARY
1
Ramesh
32
Ahmedabad
2000.00
2
Khilan
25
Delhi
2500.00
3
Kaushik
23
Kota
3000.00
4
Chaitali
25
Mumbai
7500.00
5
Hardik
27
Bhopal
8500.00
6
Komal
22
Hyderabad
4500.00
7
Muffy
24
Indore
10000.00



Now, check whether the ORDERS table is updated using the following SELECT statement −



SELECT*FROM ORDERS;



The updated ORDERS table is displayed as follows −



OID
DATE
CUSTOMER_ID
AMOUNT
102
2009-10-08 00:00:00
3
3500.00
100
2009-10-08 00:00:00
3
2000.00
101
2009-11-20 00:00:00
2
2060.00
103
2008-05-20 00:00:00
4
2560.00



UPDATE... JOIN with WHERE Clause



While updating records from multiple tables, if we use the WHERE clause along with the UPDATE... JOIN statement we can filter the records to be updated (from the combined result set).



Syntax



The syntax of SQL UPDATE... JOIN with WHERE clause in MySQL database is as follows −



UPDATEtable(s)JOIN table2 ON column3 = column4
SET table1.column1 = value1, table1.column2 = value2,...WHERE condition;



Example



Now, let us execute the following query to increase the salary of customer whose id is 3 −



UPDATE CUSTOMERS 
LEFTJOIN ORDERS 
ON CUSTOMERS.ID = ORDERS.CUSTOMER_ID 
SET CUSTOMERS.SALARY = CUSTOMERS.SALARY +1000WHERE ORDERS.CUSTOMER_ID =3;



Verification



We can verify whether the changes are reflected in a table by retrieving its contents using the SELECT statement as follows.



SELECT*FROM CUSTOMERS;



As we can see in the table below, SALARY value of "Kaushik" is increased by 1000 −



ID
NAME
AGE
ADDRESS
SALARY
1
Ramesh
32
Ahmedabad
2000.00
2
Khilan
25
Delhi
1500.00
3
Kaushik
23
Kota
3000.00
4
Chaitali
25
Mumbai
6500.00
5
Hardik
27
Bhopal
8500.00
6
Komal
22
Hyderabad
4500.00
7
Muffy
24
Indore
10000.00



The UPDATE... JOIN Clause in SQL Server



The SQL UPDATE... JOIN Clause also works in SQL Server database. But, the syntax of the query is slightly different from that of MySQL. However, the working of it is exactly the same as MySQL query.




In MySQL, the UPDATE statement is followed by the JOIN clause and SET statements respectively. Whereas, in MS SQL Server the SET statement is followed by the JOIN clause.




Syntax



Following is the syntax of the UPDATE... JOIN in SQL Server −



UPDATEtables(s)SET column1 = value1, column2 = value2,...FROM table1
JOIN table2 ON table1.join_column = table2.join_column;



Example



In this example, we will update values of the CUSTOMERS and ORDERS table that we created above; using the following UPDATE... JOIN query −



UPDATE CUSTOMERS
SET SALARY = SALARY +1000FROM CUSTOMERS 
JOIN ORDERS ON CUSTOMERS.ID = ORDERS.CUSTOMER_ID;



Verification



We can verify whether the changes are reflected in a table by retrieving its contents using the SELECT statement as follows.



SELECT*FROM CUSTOMERS;



The updated CUSTOMERS table is displayed as follows −



ID
NAME
AGE
ADDRESS
SALARY
1
Ramesh
32
Ahmedabad
2000.00
2
Khilan
25
Delhi
2500.00
3
Kaushik
23
Kota
3000.00
4
Chaitali
25
Mumbai
7500.00
5
Hardik
27
Bhopal
8500.00
6
Komal
22
Hyderabad
4500.00
7
Muffy
24
Indore
10000.00