MySQL變更多個查詢到單個查詢

Question

我有兩個MySQL表：

tblcoach：包含字段（coachid，coachschoolid，otherstuff）

tblschool：包含字段（schoolid，schooldivision）

我試圖獲得僅限於與教練處於同一學校的那些學校的學校名單。

這段代碼我有工作，但有沒有辦法產生一個單一的MySQL查詢來實現相同的結果？

SELECT @cs := coachschoolid FROM tblcoach c; 
SELECT @sd := s.schooldivision FROM tblschool s WHERE s.schoolid = @cs; 
SELECT s2.schoolid, s2.schoolname FROM tblschool s2 WHERE schooldivision = @sd 

Answer 1

巢查詢：

select schoolId, schoolname 
from tblschool 
where 
    schooldivision = (
     select schooldivision from tblschool where schoolid = (
      select coachschoolid from tblcoach 
     ) 
    ) 

Answer 2

這似乎將有1名教練工作。 您可以使用自聯接來做到這一點：

SELECT s2.schoolid, s2.schoolname 
FROM tblschool s 
INNER JOIN tblschool s2 on s.schooldivision = s2.schooldivision 
WHERE s.schoolid = ? 

允許您在schoolID通過。如果你想通過coachID：

SELECT s2.schoolid, s2.schoolname 
FROM tblschool s 
INNER JOIN tblschool s2 on s.schooldivision = s2.schooldivision 
INNER JOIN tblcoach c on c.coachschoolid = s.schoolid 
WHERE c.coachid = ?