请更正该sql查询.

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我分别从users和groups表和中获取用户名和角色名 我有第三个角色表，该表具有来自users表和groups表的userid和groupid外键. 现在，我想根据用户名和角色名将角色分配给用户(如果它不存在于数据库中).但是首先我要检查角色是否在数据库的角色表中退出. 所以我写了一个查询来实现它.其执行不正确

i am taking username and rolename from users and groups table respectively and i have a third role table which has a foreign key of userid and groupid from the users table and groups table. now i want to assing roles to users on the bases of username and rolename if it doesnot exits in the database. but first i am checking that whether the role exits or not in the role table of the database. so i write a query to implement it. its not executing properly

<pre lang="c#">"SELECT Count(UserId,GroupID) FROM roles Select UserId,GroupID from Users,Groups WHERE username = ''" + TextBox1 + "'' AND name = ''" + TextBox2.Text + "''";

有人可以帮我改正吗.

can anyone help me to correct it out.

推荐答案

尝试 Count(UserID) or Count(*)