SQL查询返回用户数

Question

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SQL查询，用于返回分配给角色名称为“管理员”的角色的用户数。

long

···

Answer 1

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

或者，更加通用和计算每个RoleName的数量

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

Answer 2

您可以尝试这样的查询

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