I have a SQL query where I get the count of something, but what I really
want is a yes/no (boolean) answer. Here is my query:
SELECT COUNT(*) AS COUNT FROM hd_entries,hier archy WHERE
IFNULL (BETWEEN_TIMES (b_yr, b_day, b_msec, e_yr, e_day, e_msec,
2001, 31, 0, 2001, 31, 63720000) >0, 1) AND
hd_entries.data _key=hierarchy. data_key AND
hierarchy.proje ct='CLUSTERII' AND
hierarchy.missi on='CLUSTER-4' AND
hierarchy.exper iment='PEACE';
Is there a way to change this such that it will only return a 0 or 1. Our
hope is that this makes the series of queries that I need to do go that much
quicker. The BETWEEN_TIMES function is a routine that I wrote that returns
a -1, 0, 1 if the entry sent in to it is between the given times.
I'm using MySQL v3.23.58 if it matters.
Thanks!
Joey 1 2106 jo**@swri.edu wrote: SELECT COUNT(*) AS COUNT FROM hd_entries,hier archy WHERE ...
Is there a way to change this such that it will only return a 0 or 1. Our hope is that this makes the series of queries that I need to do go that much quicker.
You could try fetching just one row using LIMIT. Then the query would
return an empty result set indicating a count of 0, or else a result set
of 1 row indicating a count greater than 0. This should run pretty
quick, since MySQL short-circuits when using LIMIT. Once it finds the
number of rows to satisfy the limit, it stops working on the query.
SELECT 1 AS I_FOUND_ONE
FROM hd_entries, hierarchy
WHERE ...
LIMIT 1
If you need exactly one row with a 1 or a 0, you could do the same query
as you had, but use IF() to return 1 or 0.
SELECT IF(COUNT(*) > 0, 1, 0) AS I_FOUND_ONE
FROM hd_entries, hierarchy
WHERE ...
Other solutions I could suggest involve using subqueries within the
EXISTS predicate, but you said you're using MySQL 3.23, so those
solutions won't work for you.
Regards,
Bill K. This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics |
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