在 C# 中运行 SQL 查询时出现超时异常

Question

尝试使用以下代码填充List：

string sql = ";WITH getUniqueParams AS (" +
                               "SELECT DISTINCT [a] AS 'param' FROM table " +  
                               "UNION ALL " + 
                               "SELECT DISTINCT [b] AS 'param' FROM table " + 
                               "UNION ALL " + 
                               "SELECT DISTINCT [c] AS 'param' FROM table " +  
                               "UNION ALL " + 
                               "SELECT DISTINCT [d] AS 'param' FROM table " + 
                               "UNION ALL " + 
                               "SELECT DISTINCT [e] AS 'param' FROM table " +  
                               "UNION ALL " + 
                               "SELECT DISTINCT [f] AS 'param' FROM table " +  
                               "UNION ALL " + 
                               "SELECT DISTINCT [g] AS 'param' FROM table " + 
                               "UNION ALL " + 
                               "SELECT DISTINCT [h] AS 'param' FROM table " +  
                               "UNION ALL " + 
                               "SELECT DISTINCT [i] AS 'param' FROM table " +  
                               "UNION ALL " + 
                               "SELECT DISTINCT [j] AS 'param' FROM table " +
                               "UNION ALL " + 
                               "SELECT DISTINCT [k] AS 'param' FROM table) " + 
                               "SELECT DISTINCT [param] FROM getUniqueParams ORDER BY [param]";   //the result of this statement to be stored in a string

            List<string> lUniqueParams = new List<string>();

            // set up SQL connection and command
            using (SqlConnection conn = new SqlConnection(@"Data Source=server;Initial Catalog=db;Integrated Security=SSPI"))
            using (SqlCommand cmd = new SqlCommand(sqlGetUniqueParams, conn))
            {
                conn.Open();

                // get a SqlDataReader to read multiple rows
                using (SqlDataReader rdr = cmd.ExecuteReader()) //getting exception here when debugging
                {
                    // while there are more result rows.....
                    while (rdr.Read())
                    {
                        // grab the 0-index value from the result row
                        lUniqueParams.Add(rdr.GetString(0));
                    }
                }

                conn.Close();
                conn.Dispose();
            }

我在以下代码行遇到异常：

using (SqlDataReader rdr = cmd.ExecuteReader())

我的查询在语法上不正确吗？查询表现不好，rdr是不是只读了这么久没有结果，然后给出异常？我错过了什么吗？

Answer 1

这对我有用，请检查：在查询中将表更改为 [table] 并使用 (SqlCommand cmd = new SqlCommand(sqlGetUniqueParams, conn)) 更改为使用 (SqlCommand cmd = new SqlCommand(sql, conn ))

string sql = ";WITH getUniqueParams AS (" +
                               "SELECT DISTINCT [a] AS 'param' FROM [table]" +  
                               "UNION ALL " + 
                               "SELECT DISTINCT [b] AS 'param' FROM [table]" + 
                               "UNION ALL " + 
                               "SELECT DISTINCT [c] AS 'param' FROM [table]" +  
                               "UNION ALL " + 
                               "SELECT DISTINCT [d] AS 'param' FROM [table]" + 
                               "UNION ALL " + 
                               "SELECT DISTINCT [e] AS 'param' FROM [table]" +  
                               "UNION ALL " + 
                               "SELECT DISTINCT [f] AS 'param' FROM [table]" +  
                               "UNION ALL " + 
                               "SELECT DISTINCT [g] AS 'param' FROM [table]" + 
                               "UNION ALL " + 
                               "SELECT DISTINCT [h] AS 'param' FROM [table]" +  
                               "UNION ALL " + 
                               "SELECT DISTINCT [i] AS 'param' FROM [table]" +  
                               "UNION ALL " + 
                               "SELECT DISTINCT [j] AS 'param' FROM [table]" +
                               "UNION ALL " + 
                               "SELECT DISTINCT [k] AS 'param' FROM [table]) " + 
                               "SELECT DISTINCT [param] FROM getUniqueParams ORDER BY [param]";   //the result of this statement to be stored in a string

            List<string> lUniqueParams = new List<string>();

            // set up SQL connection and command
            using (SqlConnection conn = new SqlConnection(@"Data Source=server;Initial Catalog=db;Integrated Security=SSPI"))
            using (SqlCommand cmd = new SqlCommand(sql, conn))
            {
                conn.Open();

                // get a SqlDataReader to read multiple rows
                using (SqlDataReader rdr = cmd.ExecuteReader()) //getting exception here when debugging
                {
                    // while there are more result rows.....
                    while (rdr.Read())
                    {
                        // grab the 0-index value from the result row
                        lUniqueParams.Add(rdr.GetString(0));
                    }
                }

                conn.Close();
                conn.Dispose();
            }