SQL UPDATE JOIN
is used to update the data of one table by using the data of some other table and some JOIN
conditions.
UPDATE tableName JOIN tableName ON tableName.colName = tableName.colName SET tableName.colName = tableName.colName;
Let’s look at an example to understand the concept.
Suppose we have a table Employee
with the following data:
SELECT * FROM Employee
We have another table named Manager
with the following data:
SELECT * FROM Manager
Now we write a query in which we update the values of the Employee
table by using the values of Manager
table for the rows where Age
is equal to 21
or 25
. We also want to update the Name
and the City
.
UPDATE Employee INNER JOIN Manager ON Employee.Age = Manager.Age SET Employee.Name = Manager.Name, Employee.City = Manager.City WHERE Employee.Age IN (21, 25); SELECT * FROM Employee;
Line 1: We update the Employee
table.
Line 3: We join both the tables on the basis of their age.
Lines 5 to 6: We set the name and the city of Employee
to be the same as the name and city of Manager
.
Line 7: Rows are updated only if the age equals 21 or 25.
Line 9: We display the data of the Employee
table to the console.
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