Hi, I am using MonetDB Jan2014 SP1, running on MacOS. I have a table like this. sql>select * from two; +------+---------------------------------------------------------------------------------------------- | id | name | istrue | joindate | jointime | count | +======+==================================================== | 1 | null | false | 2017-12-08 | 2014-06-30 14:05:31.000000 | 2 | | 2 | vijay | false | 2017-12-08 | 2014-06-30 14:05:59.000000 | 3 | | 3 | krish | true | 2017-12-08 | 2014-06-30 14:06:17.000000 | 5 | | 4 | bat | true | null | null | null | | 5 | gotham | false | null | null | null | | 6 | wayne | false | null | null | 3 | +------+------------------------------------------------------------------------------------------------- 6 tuples (3.504ms) I tried to do a join on this table with the same table with the following query and got this result. sql>select two.id, two.name, two.count, twoAlias.id as id2, twoAlias.name as name2 from two left join two twoAlias on two.count=twoAlias.id; +------+------------------------------------------- -------------------------------------------------------+ | id | name | count | id2 | name2 +=============================================================+ | 1 | null | 2 | 2 | vijay | | 2 | vijay | 3 | 3 | krish | | 3 | krish | 5 | 5 | gotham | | 4 | bat | null | 3 | krish | | 5 | gotham | null | null | null | | 6 | wayne | 3 | null | null | +------+-------------------------------- --------------------------------------------------------------------+ 6 tuples (5.605ms) As it could be seen clearly, *this join is clearly resulting in a wrong output* at the 4th row. *The join criterion two.count=twoAlias.id is satisfied in the first 3 rows, but are clearly violated in the 4th row*, where in the values in the join columns (count and id2 here) are clearly found to be different. Hence the join rows are not matching. I expected that the output would be +------+------------------------------------------- -------------------------------------------------------+ | id | name | count | id2 | name2 +=============================================================+ | 1 | null | 2 | 2 | vijay | | 2 | vijay | 3 | 3 | krish | | 3 | krish | 5 | 5 | gotham | | 4 | bat | null | null | null | | 5 | gotham | null | null | null | | 6 | wayne | 3 | null | null | +------+-------------------------------- --------------------------------------------------------------------+ 6 tuples (5.605ms) Is this really a bug?? Else, what would be the logic behind this? Thanks in advance. With Regards, Vijayakrishna.P. Mobile : (+91) 9500402305.