Join two tables on multiple conditions - SQL Server - sql

Question

I need to join two tables based on some conditions. The src tale in my daily input. I need to join the src table with the mstr table based on some criteria which is as below.
If I get a join between the two tables by memberid, fname and lname then I need to take the dob from the mstr table.
If I do not get a matching criteria on the above basis then I need to join just by member id and then take the dob. If there are multiple records available in the mstr by member id then I need to pick that record which has the older of the dob.
If I do not get a match by memberid also then the need to randomly create a fname which would be xx+5random numbers, lname would be ZZ+5andom numbers and dob as today's date - 110 years.
This is what I have tried which would help you expedite the solution. I am providing the sample data for both the tables
declare #src table (memberids int, fnames varchar(25), lnames varchar(25));
insert into #src values
(1, 'Ankit','Bansal'),
(2, 'Dinesh','Bansal'),
(3, 'Sushil','Dania'),
(4, '',''),
(5, Null ,Null),
(10,Null,Null)
select * from #src
declare #mstr table (memberid int, fname varchar(25), lname varchar(25),dob date);
insert into #mstr values
(1, 'Ankit','Bansal','2010-06-24'),
(2, 'Dinesh','Bansal','2009-06-24'),
(3, 'Sushil','Dania','2000-06-24'),
(4, 'Sunil','Wadh','2011-06-24'),
(5, 'Suresh','Bansal','2000-06-24'),
(5, 'Animesh','Bajaj','2001-06-24'),
(6, 'Dhiresh','Jain','2001-06-24');
select * from #mstr;
This is the query that I have written.
select memberids, fnames, lnames, a.dob
from #src
outer apply
(select dob
from #mstr where memberids = memberid and fnames = fname
and lnames = lname) a ;
The current result that I am getting is
memberids fnames lnames dob
1 Ankit Bansal 2010-06-24
2 Dinesh Bansal 2009-06-24
3 Sushil Dania 2000-06-24
4 NULL
5 NULL NULL NULL
10 NULL NULL NULL
However the output should look like below
memberids fnames lnames dob
1 Ankit Bansal 24-06-2010
2 Dinesh Bansal 24-06-2009
3 Sushil Dania 24-06-2000
4 Sunil Wadh 24-06-2011
5 Suresh Bansal 24-06-2000
10 XX12345 ZZ123456 Today's Date - 110 years

Answer 1

I believe the following will do (tested on SQL Fiddle):
SELECT #src.memberids
, CASE WHEN a.memberid IS NOT NULL THEN #src.fnames
WHEN b.memberid IS NOT NULL THEN b.fname
ELSE 'XX' + FORMAT(ABS(CAST(CHECKSUM(NewId()) AS BIGINT)) % 100000, '00000')
END AS fnames
, CASE WHEN a.memberid IS NOT NULL THEN #src.lnames
WHEN b.memberid IS NOT NULL THEN b.lname
ELSE 'ZZ' + FORMAT(ABS(CAST(CHECKSUM(NewId()) AS BIGINT)) % 100000, '00000')
END AS lnames
, CASE WHEN a.memberid IS NOT NULL THEN a.dob
WHEN b.memberid IS NOT NULL THEN b.dob
ELSE DATEADD(year, -110, CAST(GETDATE() AS DATE))
END AS dob
FROM #src
LEFT JOIN #mstr a ON a.memberid = #src.memberids
AND a.fname = #src.fnames
AND a.lname = #src.lnames
OUTER APPLY (
SELECT TOP 1 b.memberid, b.fname, b.lname, b.dob
FROM #mstr b
WHERE b.memberid = #src.memberids
ORDER BY b.dob
) b

Answer 2

Please check this query. This should work but I must say that there are flaw in table design. If this is the requirement, consider the following query. But if you have scope, you can rethink to redesign your table first.
declare #src table (memberids int, fnames varchar(25), lnames varchar(25));
insert into #src values
(1, 'Ankit','Bansal'),
(2, 'Dinesh','Bansal'),
(3, 'Sushil','Dania'),
(4, '',''),
(5, Null ,Null),
(10,Null,Null)
declare #mstr table (memberid int, fname varchar(25), lname varchar(25),dob date);
insert into #mstr values
(1, 'Ankit','Bansal','2010-06-24'),
(2, 'Dinesh','Bansal','2009-06-24'),
(3, 'Sushil','Dania','2000-06-24'),
(4, 'Sunil','Wadh','2011-06-24'),
(5, 'Suresh','Bansal','2000-06-24'),
(5, 'Animesh','Bajaj','2001-06-24'),
(6, 'Dhiresh','Jain','2001-06-24');
SELECT M.memberid,M.fname,M.lname,M.dob
FROM (
SELECT M.memberid, MIN(M.dob) dob
FROM #src S
INNER JOIN #mstr M ON S.memberids = M.memberid
AND S.fnames = M.fname
AND S.lnames = M.lname
GROUP BY M.memberid
)B
INNER JOIN #mstr M ON B.memberid = M.memberid AND B.dob = M.dob
UNION
SELECT M.memberid,M.fname,M.lname,M.dob
FROM (
SELECT M.memberid, MIN(M.dob) dob
FROM #src S
INNER JOIN #mstr M ON S.memberids = M.memberid
AND (S.fnames IS NULL OR S.fnames = '')
GROUP BY M.memberid
)B
INNER JOIN #mstr M ON B.memberid = M.memberid AND B.dob = M.dob
UNION
SELECT C.smid memberids, 'XX'+CAST ((convert(numeric(5,0),rand() * 10000) + 9999)AS VARCHAR(5)) fname,
'ZZ'+CAST ((convert(numeric(5,0),rand() * 10000) + 9999)AS VARCHAR(5)) lnames,
DATEADD(YY,-110, GETDATE()) dob
FROM
(
SELECT S.memberids smid,M.memberid mmid
FROM #src S
LEFT JOIN #mstr M ON S.memberids = M.memberid
)C WHERE
C.smid IS NOT NULL
AND C.mmid IS NULL