SQL UPDATE Statement
SQL Update Statement :
- In SQL we can use update statement to update the existing records or any field of the database.
- In SQL update statement we must use where condition otherwise the complete database will be altered by UPDATE statement.
SQL UPDATE Syntax :
UPDATE table_name SET column1 = value1, column2 = value2, ... WHERE column_name = some_value;
In the above syntax we want to update the column1 with the value value1. Where condition is used to select the appropriate record to be updated.
Demo Database :
Consider the following demo table -
+----+----------+-----+-----------+----------+ | ID | ENAME | AGE | ADDRESS | SALARY | +----+----------+-----+-----------+----------+ | 1 | Ramesh | 32 | Kota | 2000.00 | | 2 | Raj | 23 | Delhi | 1500.00 | | 3 | Anand | 21 | Karachi | 2000.00 | | 4 | Saurabh | 25 | Mumbai | 6500.00 | | 5 | Poonam | 29 | Bhopal | 8500.00 | | 6 | Komal | 23 | Pune | 4500.00 | | 7 | Omkar | 24 | Indore | 10000.00 | +----+----------+-----+-----------+----------+
SQL UPDATE Statement :
UPDATE employee SET ENAME ='Raman',ADDRESS='Pune' WHERE ID = 1;
In this example we are going to update the record having ID = 2 with the Ename = “Raman” and Address = “Pune”.
+----+----------+-----+-----------+----------+ | ID | ENAME | AGE | ADDRESS | SALARY | +----+----------+-----+-----------+----------+ | 1 | Raman | 32 | Pune | 2000.00 | | 2 | Raj | 23 | Delhi | 1500.00 | | 3 | Anand | 21 | Karachi | 2000.00 | | 4 | Saurabh | 25 | Mumbai | 6500.00 | | 5 | Poonam | 29 | Bhopal | 8500.00 | | 6 | Komal | 23 | Pune | 4500.00 | | 7 | Omkar | 24 | Indore | 10000.00 | +----+----------+-----+-----------+----------+
Above result will be obtained after the update statement execution.
Precaution to be take :
Please make sure that you are selecting particular record or record set using where condition. You should avoid using below query -
UPDATE employee SET ENAME ='Raman',ADDRESS='Pune';
it will results into -
+----+----------+-----+-----------+----------+ | ID | ENAME | AGE | ADDRESS | SALARY | +----+----------+-----+-----------+----------+ | 1 | Raman | 32 | Pune | 2000.00 | | 2 | Raman | 23 | Pune | 1500.00 | | 3 | Raman | 21 | Pune | 2000.00 | | 4 | Raman | 25 | Pune | 6500.00 | | 5 | Raman | 29 | Pune | 8500.00 | | 6 | Raman | 23 | Pune | 4500.00 | | 7 | Raman | 24 | Pune | 10000.00 | +----+----------+-----+-----------+----------+
It will update all the records of the database.