SQL查詢返回的用戶

Question

SQL查詢的

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數返回分配與角色名「管理員」角色的用戶數。

SELECT RoleName count(*) 
FROM Roles 
WHERE RoleName = ‘Administrators’; 

?????

Answer 1

SELECT RoleName, count(*) as NumberOf 
FROM Roles 
WHERE RoleName = ‘Administrators’; 

或者，更普遍和計數的每個角色名

SELECT RoleName, count(*) as NumberOf 
FROM Roles 
GROUP BY RoleName 

Answer 2

號你可以嘗試這樣的

SELECT 
    r.RoleName, 
    COUNT(UR.Userid) 
FROM Roles R 
JOIN UserRole UR 
    ON R.RoleId = UR.RoleId 
GROUP BY r.RoleName