Question

   public void InsertUserReputation()
{
    StringBuilder sb = new StringBuilder();
    sb.Append("UPDATE u ");
    sb.Append(" SET u.Reputation = (u.Reputation + @Reputation)");//Problem is here u.Reputation is "Null" not 0... I think i need some if statement to check if it is a null and then update it to 0 and then add..what do you think?
    sb.Append(" FROM Users u");
    sb.Append(" INNER JOIN Comments c ON c.UsersID = u.UsersID");
    sb.Append(" WHERE c.CommentsID = @CommentsID");

    using (SqlConnection conn = new SqlConnection(AllQuestionsPresented.connectionString))
    {
        SqlCommand cmd = new SqlCommand(sb.ToString(), conn);
        cmd.Parameters.Add("@Reputation", SqlDbType.Int).Value = 5;
        cmd.Parameters.Add("@CommentsID", SqlDbType.Int).Value = commentID;  
        conn.Open();
        cmd.ExecuteNonQuery();
    }
}

我想为用户添加5分的声誉，因为他在帖子中留下了评论。但是它无法更新原因？/ ... commentID确实获得了一个值，因此信誉参数

Answer 1

更改

SET u.Reputation = (u.Reputation + @Reputation)

成：

SET u.Reputation = COALESCE(u.Reputation,0) + @Reputation

所以NULL字段中的Reputation在添加0之前已更改为@Reputation。

或者，如果您首先将所有NULL值设置为0，然后使用语句ALTER TABLE创建字段NOT NULL，则可以保留代码。执行以下操作，一次：

UPDATE Users
SET Reputation = 0
WHERE Reputation IS NULL ;

ALTER TABLE Users 
ALTER COLUMN Reputation NOT NULL DEFAULT 0 ;

Answer 2

sb.Append(" SET Reputation = (u.Reputation + @Reputation)");

编辑：我错过了关于你的原始笔记。可能是空的。尝试下一步：

sb.Append(" SET Reputation = (isnull(u.Reputation,0) + @Reputation)");

Answer 3

你也可以改变

SET u.Reputation = (u.Reputation + @Reputation)

到

SET u.Reputation = COALESCE(u.Reputation + @Reputation, @Reputation, 0)

但所有现有答案都能很好地满足您的需求

上面提供的唯一好处是，如果@Reputation也是NULL，它仍然有效。

SQL update语句添加值

3 个答案: