Google Spreadsheet: Query String and Numeric (Involving math formula)

Question

Sorry about the imprecise title. Allow me to elaborate. I'm currently in the process of making 'Order' sheets for the small retailer i work for. Some items are easy to count due to low inventory while other items are abundant and difficult to count but easy to gauge whether we ought to order them.

When an employee takes a store count, the on-hand number they put down is contrasted with a minimum. The minimum is our lower threshold. The minimum is subtracted by the input quantity and a formula produces a third column, "Order". If the number in the order column is < 0 then a query function on a separate sheet will copy the entire row. To be clear, there are three columns, "On Hand", "Minimum", "Order", with the "Order" column containing the following mathematical formula:

="Minimum" - "On Hand" 
[Cells are specified so that it would look more like "=B2-A2".]

However, I'd also like to include the ability for employees to put a simple 'x' in the count spot, signifying that we need to order the product without having to count every single instance of the item. I'd still like to include the ability for them to enter a number if they so choose. I'd like for them to be able either the number or the 'x' in the same column. I'm currently using the following query function:

=QUERY('String(Fail)'!A:D;"select * where A contains 'x' or C > 0")

[The above is from a sheet I'm experimenting with. I will provide a link below in case you're more hands-on.]

The issue arises when the formula in the "order" column outputs any sort of number. If the formula is functional, no row marked with an 'x' is copied to the new page via the query command. If any row produces a numeric, no 'x' rows are copied over at all. I've experimented a bit but am at a loss as to where to go next.

The sheet I'm currently experimenting with is linked below. If you'd like any additional information I'd be happy to provide it. I'm relatively new to all of this so excuse my stupidity. I do recognize that I could very likely make a script for this but am not well versed in scripting with Google Apps and enjoy the immediate benefits of the query function.

Any help is welcome. Thank you.

Experimental Spreadsheet

Answer 1

All the values in a column need to be of the same type in order to be evaluated by QUERY. The mix of 'x' and numbers is confusing things.

If you use the Format menu to ensure all the values in column A are Plain Text, then your Query will work. (Formatting a numeric value as plain text does not stop it from working in a numeric calculation, so your column C survives.) Here's a screenshot of your query, after doing that formatting:

Based on your specification, your query needs to have the comparison to zero reversed, like this:

=QUERY('String(Fail)'!A:D;"select * where A contains 'x' or C < 0")
                                                             ^^^