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SQL Command: UPDATE

• An UPDATE statement is an SQL command used to update the data values of specified rows in database tables. It has the syntax:

  UPDATE items SET name=‘Blue T-Shirt’, price=8.99 WHERE itemID=1001;

• Its WHERE clause operates just like for SELECT statements to be able to select specific rows from a table. It can thus also use comparison & logical operations in its where condition.
• To update column values for all rows in a table, the WHERE clause is simply omitted:

  UPDATE items SET imageFileExt=‘jpg’;

• Running an UPDATE query from PHP works the same way as running an INSERT query from PHP because it does not return a result set. To process an UPDATE query's results:
  • The result of the query() method can be tested for its truth value to test the success of the UPDATE.
  • The MySQLi->affected_rows property can also be accessed to get the number of rows that were updated.
• htmlspecialchars() is a built-in PHP function that will encode any HTML special characters within a string as proper HTML entities. The function will encode the following special characters by default:
  • “ – becomes "
  • < - becomes <
  • > - becomes >
  • & – becomes &
• addslashes() is a built-in PHP function that is used to escape characters that should be escaped in database queries. It will escape the following characters:
  • ‘ – escaped as \’
  • “ – escaped as \”
• Additional Resources:
  • SQL Command Reference - UPDATE
  • Function Reference - htmlspecialchars()
  • Function Reference - addslashes()