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SQL UPDATE statement

UPDATE statement is used to update records in a table.

SQL UPDATE statement

UPDATE statement to update the table in the existing record.

SQL UPDATE Syntax

UPDATE table_name
SET column1 = value1 , column2 = value2 ,...
WHERE some_column = some_value ;

lamp Note that SQL UPDATE statement WHERE clause!
WHERE clause specifies which record or records which need to be updated. If you omit the WHERE clause, all records will be updated!

The demo database

In this tutorial, we will use w3big sample database.

The following is a selected "Websites" table data: 

+----+--------------+---------------------------+-------+---------+
| id | name         | url                       | alexa | country |
+----+--------------+---------------------------+-------+---------+
| 1  | Google       | https://www.google.cm/    | 1     | USA     |
| 2  | 淘宝          | https://www.taobao.com/   | 13    | CN      |
| 3  | 本教程      | http://www.w3big.com/    | 4689  | CN      |
| 4  | 微博          | http://weibo.com/         | 20    | CN      |
| 5  | Facebook     | https://www.facebook.com/ | 3     | USA     |
+----+--------------+---------------------------+-------+---------+

Examples of SQL UPDATE

Suppose we want to "tutorial" alexa ranking updated to 5000, country to USA.

We use the following SQL statement:

Examples

UPDATE Websites SET alexa = '5000', country = 'USA' WHERE name = 'tutorial';

Execute the above SQL, then read the "Websites" list, the data is as follows:


Update WARNING!

When updating records to be extra careful! In the example above, if we omit the WHERE clause as follows:

UPDATE Websites
SET alexa = '5000', country = 'USA'

Websites will execute the code above the table all the data alexa to 5000, country to USA.

UPDATE WHERE clause does not perform to be careful, then be careful.