10.3. I am using SQL, and Interchange is slow ...

It isn't Interchange. First of all, did you index your 'SKU' or other key fields? The reason Interchange doesn't do it for you is that every SQL database seems to do that a bit differently. Even then, you can try Interchange's COLUMN_DEF parameter:

Database products COLUMN_DEF code=char(16) PRIMARY KEY

This will at least index the code field for MySQL. Other databases differ.

Interchange can return VERY fast SQL search results. But you need to at least give it something to work with. The proper method for fast selection is:

[query sql="select code,category,title,price from products" ]

Category: [sql-param category]<BR>
Title:    <A HREF="[area [sql-code]]"> [sql-param title] </A><BR>
Price:    <A HREF="[area order [sql-param 0]]"> [sql-param price] </A><BR>


This is especially powerful when you consider a joined query like:

       SELECT code, price, title, extended.desc
       FROM   products, extended
       WHERE  products.category = 'Renaissance'

Note that the extended.desc field will be accessed as [sql-param desc]. Don't forget that you must index your fields if you want fast searching with them as a criteria.