how to limit row number to one unique row in SQL query? - sql

Question

I need to limit the row number to one unique row in SQL query. Here's sample data to recognize what I'm talking about:
john doe 3000 fog horn drive , ky 40444
john doe 3001 merry lane , ky 40484
I want to return the first one in the list here's my query :
Select
DISTINCT p.personID, e.citizenship,
rtrim(i.lastname + CASE WHEN i.suffix IS NULL THEN '' ELSE ' ' + i.suffix END) + ', ' + i.firstname + (CASE WHEN i.middlename IS NULL THEN '' ELSE ' ' + i.middlename END) StuName,
e.grade, i.gender, p.studentNumber, e.citizenship, e.adult, i.birthdate,
e.disability1, e.disability2, ad.city, e.displacedHomemaker, e.homeSchooled,
e.localStudentNumber, e.migrant, e.modifiedDate, e.modifiedByID,
rtrim(Staff.lastname + CASE WHEN Staff.suffix IS NULL THEN '' ELSE ' ' + Staff.suffix END) + ', ' + Staff.firstname + (CASE WHEN Staff.middlename IS NULL THEN '' ELSE ' ' + Staff.middleName END) Staffname,
Staff.personID Staffid, i.lastname, i.firstname, i.middlename, i.ssn,
ad.phone, ad.state, ad.zip, ad.addressLine1
FROM
Person p
LEFT join
Enrollment e ON e.personID = p.personID And isnull(e.noshow, 0) = 0
LEFT join
EnrollmentKY ky ON ky.enrollmentID = e.enrollmentID
LEFT join
[Identity] i ON i.identityID = p.currentIdentityID And i.personID = p.personID
INNER join
Calendar c ON c.calendarID = e.calendarID
INNER join
SchoolYear sy ON sy.endYear = c.endYear AND sy.active = 1
JOIN
staffMember Staff ON Staff.personID = e.modifiedByID
--join view_students s ON s.personID = i.personID
left join
v_MailingAddress ad ON ad.personID = i.personID And ad.relatedBy = 'household'
And ad.endDate IS NULL And isnull(ad.secondary, 0) = 0
order by
i.lastname, i.firstname, i.middlename
edit: need to only pick first row in SQL code because I have a problem with people that have multiple addresses it puts two rows for them and i only need first row of data for the person that has multiple addresses.

Answer 1

If the personId is distinct for each of the records and they just have a different address, then you can add a field for the row_number() and then only select the records where the row_number = 1:
select *
from
(
Select p.personID,
e.citizenship,
rtrim(i.lastname + CASE WHEN i.suffix IS NULL THEN '' ELSE ' ' + i.suffix END) + ', ' + i.firstname + (CASE WHEN i.middlename IS NULL THEN '' ELSE ' ' + i.middlename END) StuName,
e.grade,
i.gender,
p.studentNumber,
e.citizenship,
e.adult,
i.birthdate,
e.disability1,
e.disability2,
ad.city,
e.displacedHomemaker,
e.homeSchooled,
e.localStudentNumber,
e.migrant,
e.modifiedDate,
e.modifiedByID,
rtrim(Staff.lastname + CASE WHEN Staff.suffix IS NULL THEN '' ELSE ' ' + Staff.suffix END) + ', ' + Staff.firstname + (CASE WHEN Staff.middlename IS NULL THEN '' ELSE ' ' + Staff.middleName END) Staffname,
Staff.personID Staffid,
i.lastname,
i.firstname,
i.middlename,
i.ssn,
ad.phone,
ad.state,
ad.zip,
ad.addressLine1,
row_number() over(partition by p.personid order by p.personid) rn -- add this field
FROM Person p
LEFT join Enrollment e
ON e.personID = p.personID
And isnull(e.noshow,0)=0
LEFT join EnrollmentKY ky
ON ky.enrollmentID = e.enrollmentID
LEFT join [Identity] i
ON i.identityID = p.currentIdentityID
And i.personID = p.personID
INNER join Calendar c
ON c.calendarID = e.calendarID
INNER join SchoolYear sy
ON sy.endYear = c.endYear
AND sy.active = 1
JOIN staffMember Staff
ON Staff.personID = e.modifiedByID
--join view_students s ON s.personID = i.personID
left join v_MailingAddress ad
ON ad.personID = i.personID
And ad.relatedBy = 'household'
And ad.endDate IS NULL
And isnull(ad.secondary,0)=0
) x
where x.rn = 1
order by x.lastname, x.firstname, x.middlename

Answer 2

Try using the LIMIT to limit the no. of outputs.
Eg:
SELECT COLUMN_NAME
FROM TABLE
ORDER BY CONDITION
LIMIT NO_OF_ROWS;

Answer 3

Have you tried using a "GROUP BY" clause instead of the DISTINCT keyword?
Also, what about a Sub-Query? If I were writing this type of thing I'd use a sproc and create a temporary table.

Answer 4

Edit: Deleted original answer as question was changed and original answer is not the way to go with changed question.
Suggest GROUP BY clause per Neil Hoskins.