On Wed, Oct 10, 2012 at 10:53 AM, Hamish Symington < ham...@lightbluesoftware.com> wrote:
> > I was under the impression that the order of fields in the ON clause > doesn't matter. Is this impression incorrect? > It doesn't matter for the answer. You get the same result either way, right? Just one way is faster than the other. If interchanging the order of terms in an ON clause makes a performance difference, that means that there are (at least) two possible ways of evaluating the query. SQLite is looking at both possible plans and estimating the run-time for each, and it is coming up with the same estimate in both cases - a tie. The ambiguity is resolved in favor of the plan it looked at first. And the order in which the plans are examined is probably determined (to some extent) by the order of the terms in the ON clause. If you run ANALYZE on your database, SQLite will have more information with which to estimate the run-time of each plan, and is more likely to choose the faster on. At the very least, it much less likely for the estimated run-times to tie. Even better is if you compile with SQLITE_ENABLE_STAT3 and then run ANALYZE. -- D. Richard Hipp d...@sqlite.org _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
