Dennis Volodomanov <denn...@conceiva.com> wrote: > I was wondering whether the SQLite parser will parse out redundant > conditions out of an SQL statement or will it process them as if they > are all unique?
In my experience, SQLite doesn't eliminate such redundant clauses, nor remove trivial conditions (like 1=1 or 1 != 0), nor shortcircuit logical operations, nor hoist common subexpressions (those that don't depend on the current row) out of the loop. An expression is translated into VDBE program in a very literal manner. > I'm building dynamic SQL statements and sometimes I can't avoid > (well, without re-working a lot of code) things like: > > SELECT * FROM TABLEA WHERE COLUMNA=1 AND COLUMNA=1 AND COLUMNA=1 AND > ( COLUMNB=2 OR COLUMNC=3 ) > > Does it hurt performance having 3 COLUMNA statements like that in any > way? I suspect that any inefficiency introduced by that will be immeasurably small. But, if in doubt, test it. Igor Tandetnik _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
