How to get unique result from below entry? - php

Question

plan_id | elementclass | table_no | ress_id | UserID | Status
1 | elementclass1 | 1 | 0 | 0006100022 | N
1 | elementclass1 | 1 | 2 | 0006100022 | N
1 | elementclass2 | 2 | 0 | 0006100021 | N
1 | elementclass4 | 3 | 0 | 0006100023 | N
in above row I am expecting as this
if row is having same elementclass,table_no but different ress_id in that condition only take that row which is non zero.If with above condition tow rows having 0 it can take any row .if both rows have non zero then also it can take any one.
Now
for rest of others it can take values with 0.We can use group by to plan_id as there may be multiple plans.
Desired result
plan_id | elementclass | table_no | ress_id | UserID | Status
1 | elementclass1 | 1 | 2 | 0006100022 | N
1 | elementclass2 | 2 | 0 | 0006100021 | N
1 | elementclass4 | 3 | 0 | 0006100023 | N
Please help.
thanks

Answer 1

SELECT * FROM TableName a
WHERE a.ress_id = (SELECT MAX(b.ress_id) FROM TableName b WHERE b.table_no = a.table_no)
GROUP BY a.plan_id,a.table_no
This gives you:
1 result per plai_id and table_no
each result has biggest ress_id in it

Answer 2

First get the maximum ress id per element class. Then select the related records. There may be duplicates. Hence group by element class and ress id.
The following statement does not precisely do what you asked for, but maybe it suffices. In case of a tie you won't get one of the records, but one of the records' plan ids, one of the records' table nos, one of the records' user ids and one of the records' statusses. So the user id may be taken from one record and the status from another when elementclass and ress_id are equal.
select plan_id, mytable.elementclass, table_no, mytable.ress_id, userid, status
from mytable
join
(
select elementclass, max(ress_id) as max_ress_id
from mytable
group by elementclass
) agg on agg.elementclass = mytable.elementclass and agg.max_ress_id = mytable.res_id
group by mytable.elementclass, mytable.ress_id;
(It is possible to write a statement to access complete records in case of ties, but this is much more complicated - at least in MySQL.)

Answer 3

Try this:
SELECT T1.*
FROM TableName T1 JOIN
(SELECT elementclass,table_no,MAX(ress_id) as ress_id
FROM TableName
GROUP BY elementclass,table_no
)T2 ON T1.elementclass=T2.elementclass AND T1.table_no=T2.table_no AND T1.ress_id=T2.ress_id
Explanation:
Here, we are creating a temporary table T2 with maximum of ress_id for each elementclass and table_no. Then we join this table with the original table with these 3 fields and select all records from the original table T1.
Result:
PLAN_ID ELEMENTCLASS TABLE_NO RESS_ID USERID STATUS
-------------------------------------------------------------------
1 elementclass1 1 2 0006100022 N
1 elementclass2 2 0 0006100021 N
1 elementclass4 3 0 0006100023 N
See result in SQL Fiddle.