What is an UPDATE QUERY?
The SQL UPDATE statement is used to modify the data in tables’ records. A condition determines which rows are to be updated. The WHERE clause is used to specify conditions.
UPDATE table_name SET column_name = expression WHERE condition
- table_name: name of the table
- column_name: name of first, second, third column…
- expression: new value for first, second, third column…
- condition: condition to select the rows for which the values of columns need to be updated.
Here we have a Student table.
- Updating single value:
Query for updating only a single field in the Student table based on Student_Id.
UPDATE Student SET LastName = 'Kumar' WHERE Student_Id = '22'
- Updating multiple values:
Query for updating multiple values in a single statement based on the Student_Id.
UPDATE Student SET FirstName='Adiba', COURSE='BBA' where Student_Id=12;
- Omitting WHERE clause:
If we leave out the WHERE clause in the update query, all of the rows will be updated.
UPDATE Student SET Course = 'MBA'
As we can notice, Course field for all three students is updated with “MBA”, due to the omission of where clause.
Incrementing Integer Value using UPDATE Query
To increment an integer value with the UPDATE command, we use the SET clause with the + operator to add the desired value to the column’s existing value. Here’s an illustration:
UPDATE Product SET Quantity = Quantity+10;
After executing this query the quantity of all the items will get incremented by 10.
Note: also read about SQL: INSERT Query
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