动态选择值

Question

Example:

$user_input = $_POST['input'];
'SELECT '.$user_input.' FROM table_name'

So it's selecting a column in a database based on a secure (this example isn't secure obviously) value. Is this practical/allowable code?

Answer 1

In SQL you simply send a string to the DBMS (like MySQL). Because of this you can build any string you want and submit it to the DBMS.

You just have to make sure the resulting SQL query is valid. That means that e.g. the columns exist and that no invalid symbol appears.