c# - Convert.ToString 返回 `System.Byte[]` 而不是实际数据，因为 GROUP_CONCAT 返回 BLOB

Question

我有一种方法是调用MySQL过程。以下是部分程序：

SELECT AR.alert_id AS AlertId,
        AR.rule_id AS RuleId,
        AR.name AS RuleName,
        AR.rule_type AS RuleType, 
        AR.description AS Description, 
        (SELECT group_concat(occured_event_id separator ', ') 
            FROM alert_rule_event
            WHERE alert_rule_id = AR.id) AS OccuredEventIds,
FROM alert_rule AR

C#代码：

alertRuleEntity.AlertId = Convert.ToInt32(dtAlertRuleEntityList.Rows[index]["AlertId"]);
alertRuleEntity.RuleId = Convert.ToInt32(dtAlertRuleEntityList.Rows[index]["RuleId"]);
alertRuleEntity.RuleName = Convert.ToString(dtAlertRuleEntityList.Rows[index]["RuleName"]);
alertRuleEntity.RuleType = Convert.ToString(dtAlertRuleEntityList.Rows[index]["RuleType"]);
alertRuleEntity.Description = Convert.ToString(dtAlertRuleEntityList.Rows[index]["Description"]);
alertRuleEntity.OccuredEventIds = Convert.ToString(dtAlertRuleEntityList.Rows[index]["OccuredEventIds"]);

它返回值如下：

它能够正确读取所有列值。但是在列的情况下，OccuredEventIds它给出的值System.Byte[]而不是它的实际值。可能是什么问题呢？

Answer 1

在对我的程序进行以下更改后，它起作用了：

(SELECT group_concat(CONVERT(occured_event_id, CHAR(8)) separator ', ') 
FROM alert_rule_event
WHERE alert_rule_id = AR.id) AS OccuredEventIds

Answer 2

我会尝试将您的参数转换group_concat为varchar第一个，因为文档说它将二进制参数转换为BLOB.

SELECT AR.alert_id AS AlertId,
        AR.rule_id AS RuleId,
        AR.name AS RuleName,
        AR.rule_type AS RuleType, 
        AR.description AS Description, 
        (SELECT group_concat(cast(occured_event_id as char(20)) separator ', ') 
            FROM alert_rule_event
            WHERE alert_rule_id = AR.id) AS OccuredEventIds,
FROM alert_rule AR

Answer 3

Group_Concat 返回 BLOB 类型，所以只有你得到 Bytes 作为输出，

溶胶-1：

group_concat_max_len将系统变量的值更改为512 并重启MySql服务

见这里： 为什么 GROUP_CONCAT 返回 BLOB？

或者

溶胶-2：

"respect binary flags=false;"在您的连接字符串中设置

希望这可以帮助你....