Question

This is what I have:

drop table ttemp
create table ttemp(
col1 char(10),
col2 varchar(100))

INSERT INTO ttemp VALUES('101','shshsfhgs')
INSERT INTO ttemp VALUES('102','ertqehwrgs')
INSERT INTO ttemp VALUES('0102','witpipqcqp')
INSERT INTO ttemp VALUES('0103','retrtyhwqpp')


drop table #temp1
create table #temp1
(ref1 char(10),
 refdata varchar(100))

drop table #temp2
Create table #temp2
(ref1 char(10),
 refdata varchar(100))

insert into #temp1 values(101,'aaaaaaaaaaaaaa')
insert into #temp1 values(102,'bbbbbbbbbbbbbb')
insert into #temp1 values(103,'cccccccccccccc')

select * from #temp1

insert into #temp2
SELECT t1.col1, #temp1.refdata
FROM ttemp t1 
INNER JOIN #temp1 on t1.col1 = #temp1.ref1 OR t1.col1 = '0' + #temp1.ref1


select * from #temp2

What I would LIKE to have, is to get back only 1 row for each value in #temp1.
So if I have 102 in #temp1, and 102 in ttemp I should see that row. (NOT 0102)
If I have 103 in #temp1, but only 0103 in ttemp, then I should see that row (because there is no 103 in ttemp).
So I just want to prioritize the INNER JOIN: if t1.col1 = #temp1.ref1, then just use that one; not the t1.col1 = ‘0’ + #temp1.ref1.

The SELECT from #temp2 shows this now:

ref1    refdata
101         aaaaaaaaaaaaaa
102         bbbbbbbbbbbbbb
0102        bbbbbbbbbbbbbb
0103        cccccccccccccc

And I want this:

ref1    refdata
101         aaaaaaaaaaaaaa
102         bbbbbbbbbbbbbb
0103        cccccccccccccc

Answer 1

If you do it in 2 steps it is quite easy:

1. Insert high priority rows into the output table first
2. Insert low priority rows into the output table excluding any that are already
   present from the first insert. (Achieved with a left join in this case)

create table ttemp( 
col1 char(10), 
col2 varchar(100)) 

INSERT INTO ttemp VALUES('101','shshsfhgs') 
INSERT INTO ttemp VALUES('102','ertqehwrgs') 
INSERT INTO ttemp VALUES('0102','witpipqcqp') 
INSERT INTO ttemp VALUES('0103','retrtyhwqpp') 

create table #temp1 
(ref1 char(10), 
 refdata varchar(100)) 

    Create table #temp2 
(ref1 char(10), 
 refdata varchar(100)) 

insert into #temp1 values(101,'aaaaaaaaaaaaaa') 
insert into #temp1 values(102,'bbbbbbbbbbbbbb') 
insert into #temp1 values(103,'cccccccccccccc') 

INSERT INTO #temp2
SELECT t1.col1, t.refdata
FROM ttemp t1
INNER JOIN #temp1 t on t1.col1 = t.ref1


INSERT INTO #temp2
SELECT t1.col1, t.refdata
FROM ttemp t1
INNER JOIN #temp1 t on t1.col1 = '0' + t.ref1
LEFT JOIN #temp2 t2 ON t.ref1 = t2.ref1
WHERE ISNULL(t2.ref1,0) = 0

SELECT * FROM #temp2

drop table ttemp 
drop table #temp1 
drop table #temp2 

Results:

ref1    refdata 
101     aaaaaaaaaaaaaa 
102     bbbbbbbbbbbbbb 
0103    cccccccccccccc

Here’s another way building on Joe Stefanelli’s answer and altering it to produce the results you require:

SELECT t1.col1, COALESCE(ta.refdata,t.refdata ) [refdata]
FROM ttemp t1 
LEFT JOIN #temp1 t ON t1.col1 = t.ref1 
LEFT JOIN #temp1 ta ON t1.col1 = '0' + ta.ref1 AND ta.ref1 NOT IN (SELECT ref1 FROM ttemp INNER JOIN #temp1 ON col1 = ref1 )
WHERE ta.ref1 IS NOT NULL
OR t.ref1 IS NOT NULL

Results:

col1    refdata
101     aaaaaaaaaaaaaa
102     bbbbbbbbbbbbbb
0103    cccccccccccccc