On Nov 26, 2007, at 5:29 AM, Andrus wrote:
Under what interpretation would the results differ?
Results must differ for easy creation of LinQ-PostgreSQL driver.
If results are always the same , PostgreSQL should not allow to use
both
order of clauses.
Nicholas explains:
Assuming the ordering is the same on each of them (because Skip
and Take
make no sense without ordering, LINQ to SQL will create an order
for you,
which irritates me to no end, but that's a separate thread), they will
produce different results.
Say your query will produce the ordered set {1, 2, 3}. Let n =
1, m =
2.
The first query:
var query = query.Skip(n).Take(m);
converted to SELECT ... OFFSET n LIMIT m
Will return the ordered set {2, 3}, while the second query:
var query = query.Take(m).Skip(n);
converted to SELECT ... LIMIT m OFFSET n
Will return the ordered set {2}.
The reason for this is that in the first query, the Skip method
skips
one element, then takes the remaining two, while in the second
query, the
first two elements are taken, and then the first one is skipped.
Nice. Yet another example of an Object-Relational impedance
mismatch. SQL is declarative, not procedural.
Erik Jones
Software Developer | Emma®
erik@xxxxxxxxxx
800.595.4401 or 615.292.5888
615.292.0777 (fax)
Emma helps organizations everywhere communicate & market in style.
Visit us online at http://www.myemma.com
---------------------------(end of broadcast)---------------------------
TIP 2: Don't 'kill -9' the postmaster
