Ah, OK, I see that doing 'SELECT 1 FROM MyTable' returns a 1 for every
row, so I can see where the effort is probably going. However, 'SELECT
max(rowid) - 1 FROM MyTable' still only produces one result row
(obviously I'm experimenting with a much smaller database now). Still
need an explanation rather than just relying on my own speculation.
Cheers
guy
Guy Hindell wrote:
I have a fairly large table (10million rows) with a simple INTEGER
PRIMARY KEY AUTOINCREMENT field.
Executing 'SELECT max(rowid) FROM MyTable' is very fast, as is
'SELECT min(rowid) FROM MyTable'.
However, 'SELECT max(rowid) - min(rowid) FROM MyTable' is slow
(apparently accessing every row). Further, 'SELECT max(rowid) - 1
FROM MyTable' is slow - in fact using any constant in this expression
(including 0) results in a slow query.
Finally, 'SELECT (SELECT max(rowid) FROM MyTable') - 10' is very fast.
I am curious and would be grateful if someone can explain what is
going on here.
guy
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