How does LEFT JOIN work ?
Posted on 2003-03-16
I have a 20 table database, built around the Applications table. Each Application row will probably have a link to a row in the Organisations table. Each Organisation row might have a link to a row in the Locations table for the registered office, and another for the postal address. Also, each Application row might have a link to a row in the Categories table. And so it goes on...
I sort of understand about LEFT JOINS, but I would like to read some sort of tutorial that descibes in detail how to construct a SELECT statement that will return all data, even when a link is missing. Notice that in the above partial description, the Locations table has to be linked twice - once for the Office location, and once for the Postal address.
I've tried setting the Relationship structure in Access, then having it construct the appropriate SQL, but it quickly complains about ambiguous joins.