Question

我有这个问题：

CREATE PROCEDURE [dbo].[spGetUserAvatar]
    ( @userid int)  
     AS 
      BEGIN
        select avatar
          from t_user
             where (userID = @userid) AND (avatar<>null)
       end

以及执行此查询的C＃代码：

string ConnectionString = SafaConnectionString.ConnectionString;
    SqlConnection Connection = new SqlConnection(ConnectionString);
    SqlCommand cmd = new SqlCommand("spGetUserAvatar", Connection);
    cmd.CommandType = CommandType.StoredProcedure;
    cmd.Parameters.AddWithValue("@userid", userid);
    DataTable dt = new DataTable();
    SqlDataAdapter sda = new SqlDataAdapter();
    try
    {
        cmd.Connection = Connection;
        Connection.Open();            
       sda.SelectCommand = cmd;
        sda.Fill(dt);
        if (dt.Rows.Count > 0)
            return dt;
        else
            return null;
    }

它工作正常，但现在返回dt.Rows.Count == 0。如果是， t_users.avatar不是空的。我的查询错了吗？

Answer 1

您无法将NULL与<>运算符使用IS运算符进行比较，以验证NULL值

where userID = @userid AND avatar is not null

如何读取varbinary max sql server

1 个答案: