从子查询中选择列

Question

So say I've got a table called orders with a column zip_code and a table called provinces . provinces has the fields name , starting_zip and ending_zip (to indicate that all zip codes between starting and ending zip pertain to this province).

I need to select thousands of orders and include the name of the province they are to ship to. I've tried something like this:

SELECT orders.*, p.name
FROM orders, (SELECT name FROM provinces 
    WHERE order.zip_code >= provinces.starting_zip 
    AND order.zip_code <= provinces.ending_zip LIMIT 1) p
WHERE...

I also tried:

SELECT orders.*, p.name
FROM orders
JOIN (SELECT name FROM provinces 
    WHERE order.zip_code >= provinces.starting_zip 
    AND order.zip_code <= provinces.ending_zip LIMIT 1) p
WHERE...

Also:

SELECT orders.*, (SELECT name FROM provinces 
    WHERE order.zip_code >= provinces.starting_zip 
    AND order.zip_code <= provinces.ending_zip LIMIT 1) as name
FROM orders
WHERE...

No matter what I do though, I get an error like:

"Unknown column 'order.zip_code' in 'where clause'

It makes sense that the subselect wouldn't have the scope to access info from the main select, but any idea how I could get this to work?

Answer 1

Why don't you do it like this?

SELECT orders.*, 
(
    SELECT name 
    FROM provinces 
    WHERE orders.zip_code >= provinces.starting_zip 
    AND orders.zip_code <= provinces.ending_zip 
    LIMIT 1
) as name
FROM orders
WHERE...

I do not really see why this should be in the FROM statement. You are anyway selecting just the name column

Update

Did you see that I changed the tables name in the subquery? The FROM statement looks like this:

FROM orders

But the WHERE clause look like this:

WHERE order.zip_code >= provinces.starting_zip 
AND order.zip_code <= provinces.ending_zip

I have changed it in the query to this:

WHERE orders.zip_code >= provinces.starting_zip 
AND orders.zip_code <= provinces.ending_zip