The insertion of new rows into a database is just the start of data management. Unless your database is read-only, you will probably also need to make periodic changes to the data. The standard SQL modification statement looks like this:
UPDATEtable_name
SETcolumn1
=value1
,column2
=value2
,...
,columnN
=valueN
[WHEREclause
]
You specifically name the table you want to update and the values you
want to assign in the SET
clause, and then identify the rows to be affected in the
WHERE
clause. If you fail to specify a
WHERE
clause, MySQL will update every row in the
table.
In addition to assigning literal values to a column, you can also calculate the values. You can even calculate the value based on a value in another column:
UPDATE years SET end_year = begin_year+5
This command sets the value in the end_year
column
equal to the value in the begin_year
column plus 5
for each row in that table.