MySql IN clauses, trying to match IN list of tuples - mysql

Question

I am trying to select duplicate records based on a match of three columns. The list of triples could be very long (1000), so I would like to make it concise.
When I have a list of size 10 (known duplicates) it only matches 2 (seemingly random ones) and misses the other 8. I expected 10 records to return, but only saw 2.
I've narrowed it down to this problem:
This returns one record. Expecting 2:
select *
from ali
where (accountOid, dt, x) in
(
(64, '2014-03-01', 10000.0),
(64, '2014-04-23', -122.91)
)
Returns two records, as expected:
select *
from ali
where (accountOid, dt, x) in ( (64, '2014-03-01', 10000.0) )
or (accountOid, dt, x) in ( (64, '2014-04-23', -122.91) )
Any ideas why the first query only returns one record?

Answer 1

I'd suggest you don't use IN() for this, instead use a where exists query, e.g.:
CREATE TABLE inlist
(`id` int, `accountOid` int, `dt` datetime, `x` decimal(18,4))
;
INSERT INTO inlist
(`id`, `accountOid`, `dt`, `x`)
VALUES
(1, 64, '2014-03-01 00:00:00', 10000.0),
(2, 64, '2014-04-23 00:00:00', -122.91)
;
select *
from ali
where exists ( select null
from inlist
where ali.accountOid = inlist.accountOid
and ali.dt = inlist.dt
and ali.x = inlist.x
)
;
I was able to reproduce a problem (compare http://sqlfiddle.com/#!2/7d2658/6 to http://sqlfiddle.com/#!2/fe851/1 both MySQL 5.5.3) where if the x column was numeric and the value negative it was NOT matched using IN() but was matched when either numeric or decimal using a table and where exists.
Perhaps not a conclusive test but personally I wouldn't have used IN() for this anyway.
Why are you not determining the duplicates this way?
select
accountOid
, dt
, x
from ali
group by
accountOid
, dt
, x
having
count(*) > 1
Then use that as a derived table within the where exists condition:
select *
from ali
where exists (
select null
from (
select
accountOid
, dt
, x
from ali
group by
accountOid
, dt
, x
having
count(*) > 1
) as inlist
where ali.accountOid = inlist.accountOid
and ali.dt = inlist.dt
and ali.x = inlist.x
)
see http://sqlfiddle.com/#!2/ede292/1 for the query immediately above