On Mon, 24 Mar 2003, Correia, Carla wrote: > > Hi, > > I've got PsotgreSQL 7.3. > > My problem is joins. I've seen the syntax on joins and have sucessefully > used SQLs with joins, but I've got some other big SQL statements using many > and complex > joins. > Simplified example: > > select G.SELID, G.TEXT, > L.ID as SELLEVELID , L.SELLEVEL, L.LEVELJOIN, L.LEVELTEXT, > C.ID as KRITERIENFELDID, C.SELFLD > from G, L, C > where > and G.SELID = L.SELID (+) > and L.SELID = C.SELID (+) > and L.SELLEVEL = C.SELLEVEL (+) > > How can i write this in Postgres? As the problem is that I use one same > table for varios joins. This is a problem in Postgres. Any ideas? > > When I use the same table in say 3 or 4 joins in one SQL, is the only > solution unions?? Adn if so, the performance will certainly suffer? > I don't quite understand you question. but I presume that G, L, and C are in fact the same table. I'm not sure what you mean by the (+) more clarity is really required. If however G, L, and C are the same table this query can be rewritten as
select G.SELID, G.TEXT, L.ID as SELLEVELID , L.SELLEVEL, L.LEVELJOIN, L.LEVELTEXT, C.ID as KRITERIENFELDID, C.SELFLD from table as G, table as L, table as C where and G.SELID = L.SELID and L.SELID = C.SELID and L.SELLEVEL = C.SELLEVEL; Where table is the name of the table.... I hope that helps Peter Childs ---------------------------(end of broadcast)--------------------------- TIP 2: you can get off all lists at once with the unregister command (send "unregister YourEmailAddressHere" to [EMAIL PROTECTED])