SQL Join Ignore multiple matches (fuzzy results ok) - sql

Question

I don't even know what the name of my problem is called, so I'm just gonna put some sample data. I don't mind fuzzy results on this (this is the best way I can think to express it. I don't mind if I overlook some data, this is for approximated evaluation, not for detailed accounting, if that makes sense). But I do need every record in TABLE 1, and I would like to avoid the nulls case indicated below.
IS THIS POSSIBLE?
TABLE 1
acctnum sub fname lname phone
12345 1 john doe xxx-xxx-xxxx
12346 0 jane doe xxx-xxx-xxxx
12347 0 rob roy xxx-xxx-xxxx
12348 0 paul smith xxx-xxx-xxxx
TABLE 2
acctnum sub division
12345 1 EAST
12345 2 WEST
12345 3 NORTH
12346 1 TOP
12346 2 BOTTOM
12347 2 BALLOON
12348 1 NORTH
So if we do a "regular outer" join, we'd get some results like this, since the sub 0's don't match the second table:
TABLE AFTER JOIN
acctnum sub fname lname phone division
12345 1 john doe xxx-xxx-xxxx EAST
12346 0 jane doe xxx-xxx-xxxx null
12347 0 rob roy xxx-xxx-xxxx null
12348 0 paul smith xxx-xxx-xxxx null
But I would rather get
TABLE AFTER JOIN
acctnum sub fname lname phone division
12345 1 john doe xxx-xxx-xxxx EAST
12346 0 jane doe xxx-xxx-xxxx TOP
12347 0 rob roy xxx-xxx-xxxx BALLOON
12348 0 paul smith xxx-xxx-xxxx NORTH
And I'm trying to avoid:
TABLE AFTER JOIN
acctnum sub fname lname phone division
12345 1 john doe xxx-xxx-xxxx EAST
12345 1 john doe xxx-xxx-xxxx WEST
12345 1 john doe xxx-xxx-xxxx NORTH
12346 0 jane doe xxx-xxx-xxxx TOP
12346 0 jane doe xxx-xxx-xxxx BOTTOM
12347 0 rob roy xxx-xxx-xxxx BALOON
12348 0 paul smith xxx-xxx-xxxx NORTH
So I decided to go with using a union and two if conditions. I'll accept a null for conditions where the sub account is defined in table 1 but not in table 2, and for everything else, I'll just match against the min.

Answer 1

If I'm understanding correctly, it looks like you're trying to join on the sub column if it matches. If there's no match on sub, then you want it to select the "first" row for that acctnum. Is this correct?
If so, you'll need to left join on the full match, then perform another left join on a select statement that determines the division that corresponds to the lowest sub value for that acctnum. The row_number() function can help you with this, like this:
select
t1.acctnum,
t1.sub,
t1.fname,
t1.lname,
t1.phone,
isnull(t2_match.division, t2_first.division) as division
from table1 t1
left join table2 t2_match on t2_match.acctnum = t1.acctnum and t2_match.sub = t1.sub
left join
(
select
acctnum,
sub,
division,
row_number() over (partition by acctnum order by sub) as rownum
from table2
) t2_first on t2_first.acctnum = t1.acctnum
EDIT
If you don't care at all about which record you get back from table 2 when a matching sub doesn't exist, you could combine two different queries (one that matches the sub and one that just takes the min or max division) with a union.
select
t1.acctnum,
t1.sub,
t1.fname,
t1.lname,
t1.phone,
t2.division
from table1 t1
join table2 t2 on t2.acctnum = t1.acctnum and t2.sub = t1.sub
union
select
t1.acctnum,
t1.sub,
t1.fname,
t1.lname,
t1.phone,
min(t2.division)
from table1 t1
join table2 t2 on t2.acctnum = t1.acctnum
left join table2 t2_match on t2_match.acctnum = t1.acctnum and t2_match.sub = t1.sub
where t2_match.acctnum is null
Personally, I don't find the union syntax any more compelling and you now have to maintain the query in two places. For this reason, I'd favor the row_number() approach.

Answer 2

try to use
SELECT MIN(Table_1.acctnum) as acctnum , MIN(Table_1.sub) as sub,MIN( Table_1.fname) as fname, MIN(Table_1.lname) as name, MIN(Table_1.phone) as phone, MIN(Table_2.division) as division
FROM Table_1 INNER JOIN Table_2 ON Table_1.acctnum = Table_2.acctnum AND Table_1.sub = Table_2.sub
where Table_1.sub>0
group by Table_1.acctnum
union
SELECT MIN(Table_1.acctnum) as acctnum , MIN(Table_1.sub) as sub,MIN( Table_1.fname) as fname, MIN(Table_1.lname) as name, MIN(Table_1.phone) as phone, MIN(Table_2.division) as division
FROM Table_1 INNER JOIN Table_2 ON Table_1.acctnum = Table_2.acctnum
where Table_1.sub=0
group by Table_1.acctnum
this is the result
12345 1 john doe xxxxxxxxxx EAST
12346 0 jane doe xxxxxxxxxx BOTTOM
12347 0 rob roy xxxxxxxxxx BALLOON
12348 0 paul smith xxxxxxxxxx NORTH
if you change min to max TOP will be insted of BOTTOM on the second row

Answer 3

It may also work for you:
SELECT t1.acctnum, t1.sub, t1.fname, t1.lname, t1.phone,
ISNULL(MAX(t2.division),MAX(t3.division)) as division
FROM table_1 t1
LEFT JOIN table_2 t2 ON (t2.acctnum = t1.acctnum AND t1.sub = t2.sub)
LEFT JOIN table_2 t3 ON (t3.acctnum = t1.acctnum)
GROUP BY t1.acctnum, t1.sub, t1.fname, t1.lname, t1.phone

Answer 4

This will give your desired result, exactly (for the shown data):
Updated to not assume there is always a sub==1 value:
SELECT
T1.acctnum,
T1.sub,
T1.fname,
T1.lname,
T1.phone,
T2.division
FROM
TABLE_1 T1
LEFT JOIN
TABLE_2 T2 ON T1.acctnum = T2.acctnum
AND
T2.sub = (SELECT MIN(T3.sub) FROM TABLE_2 T3 WHERE T1.acctnum = T3.acctnum)
ORDER BY
T1.lname,
T1.fname,
T1.acctnum