获得三个联接表的列

Question

I was able to join 3 tables and count the data set, bet getting the columns on specific table it only see the 3rd table column..

 SELECT * 
 FROM `InvoiceItemTable` a 
 JOIN `InvoiceTable` b 
   ON (b.id = a.invoice) 
 JOIN `products` c 
   ON (a.product = c.id)  
 WHERE b.status='1' AND c.store = '2'
 //$invoices = $inginger->fetch(PDO::FETCH_ASSOC))
 echo $invoices['a.price'];

This price return error : Undefined index: a.price in... there is "price" in the first table(InvoiceItemTable). echo $invoices['invoice']; There is invoice in first table(InvoiceItemTable) and it returns it works I dont want to use $invoices['price'] because there is 'price' colum in the third table too and that is what it returns, I want to get the price in the first table. $invoices['price.InvoiceItemTable'] returns undefined index

Answer 1

php wont recognize $invoices['a.price']; you have to use $invoices['price'];

if you have same fieldname in multiple tables you have to create an alias

 SELECT a.price as a_price, b.price as b_price, c.price as c_price

and then you can use $invoices['a_price']

Answer 2

In general, it's much better to explicitly define your columns. In doing so you can add a specific name to the the column you're interested in (or conversely change the name of the one you're not to remove ambiguity)

For examples sake, I'm just showing the columns you've described but it would look something like.

SELECT a.price as price, c.price as product_price
FROM `InvoiceItemTable` a 
JOIN `InvoiceTable` b ON (b.id = a.invoice) 
JOIN `products` c ON (a.product = c.id)
WHERE b.status='1' AND c.store = '2';

Doing naming such as this is more work, but insulates your code from changes and more explicitly shows the reader what is being returned.