Tests updating with expressions.
function testExpressionUpdate() {
// Ensure that expressions are handled properly. This should set every
// record's age to a square of itself.
$num_rows = db_update('test')
->expression('age', 'age * age')
->execute();
$this
->assertIdentical($num_rows, 4, 'Updated 4 records.');
$saved_name = db_query('SELECT name FROM {test} WHERE age = :age', array(
':age' => pow(26, 2),
))
->fetchField();
$this
->assertIdentical($saved_name, 'Paul', t('Successfully updated values using an algebraic expression.'));
}