SQL - 如何在情况下计算唯一性？

Question

I am trying to count number of discharge prescription. The case is as follow:

Each prescription cantinas several orders so prescription number may occur several times using count alone. To count prescription numbers (not orders) I used distinct so each prescription number will be counted once. And I need to count only discharge prescription, so I put the other condition: Priority like '% discharge%'. Though this is not working correctly.

I am using this query but it keeps returning 1 which is not correct:

SELECT
    Count (distinct 
        (case when
        (PrescNo is not null)
        and (Priority like '% discharge%') 
        then 1 else null end)) as "Discharge Prescription" 
FROM Order_DIS
where PrescNo is not null
and ADM_Type='In Patient'

Table contains following column:

• (PrescNo) as Prescription number
• (Priority) as Priority
• (OrderItem) as Order
• (ADM_Type) as Admission Type

Answer 1

I am trying to count number of discharge prescription. The case is as follow:

Each prescription cantinas several orders so prescription number may occur several times using count alone. To count prescription numbers (not orders) I used distinct so each prescription number will be counted once. And I need to count only discharge prescription, so I put the other condition: Priority like '% discharge%'. Though this is not working correctly.

I am using this query but it keeps returning 1 which is not correct:

SELECT
    Count (distinct 
        (case when
        (PrescNo is not null)
        and (Priority like '% discharge%') 
        then 1 else null end)) as "Discharge Prescription" 
FROM Order_DIS
where PrescNo is not null
and ADM_Type='In Patient'

Table contains following column:

• (PrescNo) as Prescription number
• (Priority) as Priority
• (OrderItem) as Order
• (ADM_Type) as Admission Type