I am building a web application for a customer and I have a problem with a particular SQL query.

The query is:

```
select order_header.order_no,
       order_header.purchase_order_no,
       order_header.entry_date,
       order_header.delivery_date,
       order_totals.total_quantity
from   order_header,
       order_totals
where  order_header.order_no = order_totals.order_no

```

I have done some troubleshooting and this:

```
where  order_header.order_no = order_totals.order_no

```

is the problem. The SQL query with this line takes 35 seconds (causes DataTables to even time out at times) and without it it is instant.

So, I know the problem but I'm not a DBA so don't know the solution.

It's not my database, so the solution I need to send to the DBA to sort so I can continue with my job. Something like 

> 
> "Hey, would you mind doing A on B table so that C speeds up?"
> 
> 
> 

I just don't know what actually needs to be done!