MySQL查詢計算唯一ID，計數記錄數和組數（3個表）

Question

我有3個表格參與項目，patient_services和患者。 此查詢

SELECT 
    ps_user_loc AS loc, COUNT(ps_id) AS ser, Count(Distinct ps_ur) AS patient 
FROM patient_services 
GROUP BY loc 

UNION ALL 

SELECT 
    eng_user_loc AS loc, COUNT(eng_id) AS ser, Count(Distinct eng_ur) AS patient 
FROM engagements 
WHERE LENGTH(eng_ur)>0 
GROUP BY loc 

回報

 
loc   ser patient 
CABOOLTURE 354  255 
KILCOY   15  12 
RBWH   1840  476 
RBWH   34  27 
REDCLIFFE  3   3 
TPCH   11   9 

所以祿有雙打，我可以在PHP循環 計算SER但由於交戰相同的id和patient_services表計的患者不是唯一的。

如何根據位置選擇按服務數量和獨特患者進行分組，兩個表中（不是每個都像現在這樣）？

謝謝。

Answer 1

你在找什麼是一個完整的外連接。這將是兩個步驟：1.從表中獲取loc/patient對並加入，2.通過loc進行聚合。在標準SQL中：

select 
    loc, 
    sum(coalesce(ps.cnt, 0) + coalesce(e.cnt, 0)), 
    count(distinct patient) 
from 
(
    select 
    ps_user_loc as loc, 
    ps_ur as patient, 
    count(*) as cnt 
    from patient_services 
    group by ps_user_loc, ps_ur 
) ps 
full outer join 
(
    select 
    eng_user_loc as loc, 
    eng_ur as patient 
    count(*) as cnt, 
    from engagements 
    where length(eng_ur) > 0 
    group by eng_user_loc, eng_ur 
) e using (loc, patient) 
group by loc; 

不幸的是，MySQL不支持完整的外連接（並且不使用using子句）。一種方法是首先獲得所有位置/患者，然後加入：

select 
    l.loc, 
    sum(coalesce(ps.cnt, 0) + coalesce(e.cnt, 0)), 
    count(distinct l.patient) 
from 
(
    select ps_user_loc as loc, ps_ur as patient from patient_services 
    union 
    select eng_user_loc as loc, eng_ur as patient from engagements 
) l 
left outer join 
(
    select 
    ps_user_loc as loc, 
    ps_ur as patient, 
    count(*) as cnt 
    from patient_services 
    group by ps_user_loc, ps_ur 
) ps on ps.loc = l.loc and ps.patient = l.patient 
left outer join 
(
    select 
    eng_user_loc as loc, 
    eng_ur as patient, 
    count(*) as cnt 
    from engagements 
    where length(eng_ur) > 0 
    group by eng_user_loc, eng_ur 
) e on e.loc = l.loc and e.patient = l.patient 
group by l.loc;