Python Data Persistence – UPDATE Statement

Python Data Persistence – UPDATE Statement

It is possible to modify data of a certain field in a given table using the UPDATE statement. The usage syntax of the UPDATE query is as follows:


UPDATE table_name SET coll=vall, col2=val2,.., colN=valN WHERE [expression] ;

Note that the WHERE clause is not mandatory when executing the UPDATE statement. However, you would normally want to modify only those records that satisfy ing a certain condition. If the WHERE clause is not specified, all records will be modified.

For example, the following statement changes the price of ‘Printer’ to 1000Q.

sqlite> update products set price=10000 where name='Printer';
sqlite> select * from products;
Product ID                Name                 Price
  ----------                 -----------          ------  
      1                         Laptop              25000
      2                          TV                    40000
      3                         Router               2000
      4                         Scanner             5000
      5                         Printer              10000
      6                         Mobile             15000

However, if you want to increase the price of each product by 10 percent, you don’t have to specify the WHERE clause.

sqlite> update products set price=price+price*10/100;
sqlite> select * from products;
ProductID             Name                Price
 ----------             ----------          -------  
      1                      Laptop              27500
      2                      TV                     44000
      3                      Router                2200
      4                     Scanner               5500
      5                     Printer                11000
     6                      Mobile                16500