如何使用INNER JOIN更新3个表？

Question

I have 3 tables that look like this:

1. users:

   • ID
   • Name (string)
   • ageID (int)
   • descID (int)

2. users_age:

   • ageID (int)
   • age_group (string)

3. users_desc:

   • descID (int)
   • desc_text (string)

Now, I have an 'edit' form which uses INNER JOIN to display the corresponding string column in the place of ageID and descID instead of the IDs.

And a button that directs to updateUser.php to update the data. I know I can update name with:

$sql = "UPDATE users SET
        Name = '$uName',
        WHERE ID = '$uID'";

But how can I update the ageID/descID (INTEGER value) column in USERS table with the ID of ageID/descID from the age_group/desc_text equivalent ID when the form page is sending the string columns to the updateUser.php file?

I hope my explanation wasn't very confusing!

Answer 1

If the strings in the tables are unique (and they should be) you can update to the output of a SELECT statement

$sql = "UPDATE users
        SET ageID = (SELECT ageID FROM users_age WHERE age_group = '$uAgeString')
        WHERE ID = '$uID'";

You can do something analogous with the other table.

However - it would be better to get the ID from web page. Typically you do that by setting the value attribute of the option tag:

<select name='uAgeID'>
  <option value='1'>Young</option>
  <option value='2'>Middling</option>
  <option value='3'>Old</option>
</select>

That way you can have a simpler SQL statement:

$sql = "UPDATE users
        SET ageID = $uAgeString
        WHERE ID = '$uID'";