Combining results with DateDiff included - sql

Question

I have a list of places where people have been discharged and I need to stratify them by age. The query that I have currently below works, but it lists every discharge type count, by every age.
You can see how for age 0-1-2-3 there are all separate counts of discharge type based on what age. How can I make it so that it's only the dischargeType and the counts that are listed (as long as they are 18 and under)
SELECT DATEDIFF(yyyy, tblVisits.dob, tblVisits.admitdate) AS Age, tblDischarge.dischargeType, COUNT(tblDischarge.dischargeType) AS COUNTS
FROM tblVisits INNER JOIN
tblDischarge ON tblVisitsDischargeStatus = tblDischarge.dis_statID
GROUP BY DATEDIFF(yyyy,tblVisits.dob, tblVisits.Admitdate), tblDischarge.dischargeType
HAVING (DATEDIFF(yyyy,tblVisits.DOB, tblVisits.AdmitDate) <=18)

Answer 1

If you just want people aged under 18, but only one row per discharge-type...
SELECT
tblDischarge.dischargeType,
COUNT(tblDischarge.dischargeType) AS COUNTS
FROM
tblVisits
INNER JOIN
tblDischarge
ON tblVisitsDischargeStatus = tblDischarge.dis_statID
WHERE
(DATEDIFF(yyyy,tblVisits.DOB, tblVisits.AdmitDate) <=18)
GROUP BY
tblDischarge.dischargeType
If you want to group the ages into strata...
SELECT
tblDischarge.dischargeType,
CASE DATEDIFF(yyyy,tblVisits.DOB, tblVisits.AdmitDate)
WHEN <= 3 THEN '0..3'
WHEN <= 8 THEN '4..8'
WHEN <= 12 THEN '9..12'
ELSE '13..18'
END AS ageBand,
COUNT(tblDischarge.dischargeType) AS COUNTS
FROM
tblVisits
INNER JOIN
tblDischarge
ON tblVisitsDischargeStatus = tblDischarge.dis_statID
WHERE
(DATEDIFF(yyyy,tblVisits.DOB, tblVisits.AdmitDate) <=18)
GROUP BY
tblDischarge.dischargeType,
CASE DATEDIFF(yyyy,tblVisits.DOB, tblVisits.AdmitDate)
WHEN <= 3 THEN '0..3'
WHEN <= 8 THEN '4..8'
WHEN <= 12 THEN '9..12'
ELSE '13..18'
END

Answer 2

Remove the AGE in the selection and in the Group by part:
SELECT tblDischarge.dischargeType, COUNT(tblDischarge.dischargeType) AS COUNTS
FROM tblVisits INNER JOIN
tblDischarge ON tblVisitsDischargeStatus = tblDischarge.dis_statID
GROUP BY tblDischarge.dischargeType
HAVING (DATEDIFF(yyyy,tblVisits.DOB, tblVisits.AdmitDate) <=18)

Answer 3

I am not sure of your problem, but if you just want to count by dischargeType, for all people under 18, the code follows:
SELECT dis.dischargeType, COUNT(dis.dischargeType) AS COUNTS
FROM tblDischarge dis
JOIN tblVisits vst ON vst.DischargeStatus = dis.dis_statID
WHERE (DATEDIFF(yyyy,vst.DOB, vst.AdmitDate) <= 18)
GROUP BY dis.dischargeType;
Or you can use sub-query, like:
SELECT dischargeType, COUNT(dischargeType) AS COUNTS
FROM tblDischarge
WHERE dis_statID IN (
SELECT vst.DischargeStatus
FROM tblVisits vst
WHERE (DATEDIFF(yyyy, vst.DOB, vst.AdmitDate) <= 18)
)
GROUP BY dis.dischargeType;

Answer 4

Simply remove the calculation for age from the SELECT and the GROUP BY, and change the HAVING to a WHERE:
SELECT tblDischarge.dischargeType,
COUNT(tblDischarge.dischargeType) as COUNTS
FROM tblVisits
INNER JOIN tblDischarge
ON tblVisitsDischargeStatus = tblDischarge.dis_statID
WHERE (DATEDIFF(yyyy,tblVisits.DOB, tblVisits.AdmitDate) <=18)
GROUP BY tblDischarge.dischargeType