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SQL UPDATE with JOIN

SQL UPDATE JOIN means we will update one table using another table and join condition.

Let us take an example of a customer table. I have updated customer table that contains latest customer details from another source system. I want to update the customer table with latest data. In such case, I will perform join between target table and source table using join on customer ID.

Let’s see the syntax of SQL UPDATE query with JOIN statement.

  1. UPDATE customer_table
  2. INNER JOIN
  3. Customer_table
  4. ON customer_table.rel_cust_name = customer_table.cust_id
  5. SET customer_table.rel_cust_name = customer_table.cust_name

How to use multiple tables in SQL UPDATE statement with JOIN

Let’s take two tables, table 1 and table 2.

Create table1

  1. CREATE TABLE table1 (column1 INT, column2 INT, column3 VARCHAR (100))
  2. INSERT INTO table1 (col1, col2, col3)
  3. SELECT 1, 11, ‘FIRST’
  4. UNION ALL
  5. SELECT 11,12, ‘SECOND’
  6. UNION ALL
  7. SELECT 21, 13, ‘THIRD’
  8. UNION ALL
  9. SELECT 31, 14, ‘FOURTH’

Create table2

  1. CREATE TABLE table2 (column1 INT, column2 INT, column3 VARCHAR (100))
  2. INSERT INTO table2 (col1, col2, col3)
  3. SELECT 1, 21, ‘TWO-ONE’
  4. UNION ALL
  5. SELECT 11, 22, ‘TWO-TWO’
  6. UNION ALL
  7. SELECT 21, 23, ‘TWO-THREE’
  8. UNION ALL
  9. SELECT 31, 24, ‘TWO-FOUR’

Now check the content in the table.

  1. SELECT * FROM table_1
  1. SELECT * FROM table_2
Col 1 Col 2 Col 3
1 1 11 First
2 11 12 Second
3 21 13 Third
4 31 14 Fourth

 

Col 1 Col 2 Col 3
1 1 21 Two-One
2 11 22 Two-Two
3 21 23 Two-Three
4 31 24 Two-Four

Our requirement is that we have table 2 which has two rows where Col 1 is 21 and 31. We want to update the value from table 2 to table 1 for the rows where Col 1 is 21 and 31.

We want to also update the values of Col 2 and Col 3 only.

The most easiest and common way is to use join clause in the update statement and use multiple tables in the update statement.

  1. UPDATE table 1
  2. SET Col 2 = t2.Col2,
  3. Col 3 = t2.Col3
  4. FROM table1 t1
  5. INNER JOIN table 2 t2 ON t1.Col1 = t2.col1
  6. WHERE t1.Col1 IN (21,31)

Check the content of the table

SELECT FROM table 1

SELECT FROM table 2

Col 1 Col 2 Col 3
1 1 11 First
2 11 12 Second
3 21 23 Two-Three
4 31 24 Two-Four

 

Col 1 Col 2 Col 3
1 1 21 First
2 11 22 Second
3 21 23 Two-Three
4 31 24 Two-Four

Here we can see that using join clause in update statement. We have merged two tables by the use of join clause.

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