Question

Possible Duplicate:
MySQL #1054 unknown column

I need a query that will pull only records which match the user provided search query. The tricky part is that the information that the user is searching for is in another table. My application is pulling records from a table called ‘computers’. Inside ‘computers’ there’s a column that has an ID number of a printer (default_printer). All of the printer information such as name (which the user is searching for) is inside the ‘printers’ table which the user is searching for.

So naturally I need to list all computer information but at the same time resolve the ID inside the ‘computers’ table to the name inside the ‘printers’ table. Here’s the query that I’ve come up with so far:

     SELECT c.id, c.name, p.name default_printer, c.description
       FROM computers c, groups g
 INNER JOIN printers p
         ON g.default_printer = p.id OR c.default_printer = p.id
      WHERE p.name LIKE 'mfd%'

The problem is I’m getting the error: #1054 – Unknown column ‘c.default_printer’ in ‘on clause’. The ‘computers’ table has a column called ‘default_printer’.

Here’s my table schema:

Table name: computers
Columns: id, name, description, default_printer, report_date, guid

Table name: printers
Columns: id, name, path, location, description

Table name: groups
Columns: id, name, description, default_printer

I’m stuck, help!

Answer 1

Don’t mix comma notation for joins and explicit join notation, you’ll loose access to some of your alias names. If you don’t have access to the alias, you can’t refer to its columns. I’m assuming groups has a column id

Also, as noted elsewhere, I suggest you use a different name for your label ‘default_printer’ while you troubleshoot this and for clarity.

SELECT c.id, c.name, p.name the_default_printer, c.description
   FROM computers c
   INNER JOIN groups g  ON g.id = c.guid
   INNER JOIN printers p
     ON g.default_printer = p.id OR c.default_printer = p.id
  WHERE p.name LIKE 'mfd%'