mysql存储过程group_concat在游标中选择返回null

我有一个存储过程，我在循环游标中的结果。我遇到的问题是，license_attributes值在不应该出现时始终为空。如果我在存储过程之外执行select语句，或者作为调试在存储过程中执行光标外部的select语句，我会得到我期望的结果（非空值）mysql存储过程group_concat在游标中选择返回null

这是部分在光标选择总是返回NULL：

 (SELECT 
      CONCAT('{""',sf.Asset_Attribute__c.Type__c,'"": {',GROUP_CONCAT(
      '""',sf.Asset_Attribute__c.Key__c,'"":""',LOWER(sf.Asset_Attribute__c.Value__c),'""' 
      ),'}}') 
      FROM 
       sf.Asset_Attribute__c 
      WHERE 
       sf.Asset_Attribute__c.Asset__c = license_id 
      GROUP BY sf.Asset_Attribute__c.Asset__c) AS `license_attributes`

这里是存储过程的部分：

GETCLOUDACCOUNTS:BEGIN 

    DECLARE no_more_cloud_accounts_records boolean DEFAULT FALSE; 

    DECLARE company VARCHAR(255) DEFAULT null; 
    DECLARE license_status VARCHAR(50) DEFAULT null; 
    DECLARE license_id VARCHAR(18) DEFAULT null; 
    DECLARE cloud_owner_email VARCHAR(255) DEFAULT null; 
    DECLARE entitlement_plan VARCHAR(255) DEFAULT null; 
    DECLARE role VARCHAR(500) DEFAULT null; 
    DECLARE is_trial BOOLEAN DEFAULT false; 
    DECLARE license_attributes VARCHAR(2000) DEFAULT null; 
    DECLARE zuora_account_id VARCHAR(100) DEFAULT ''; 
    DECLARE zuora_account_number VARCHAR(50) DEFAULT null; 
    DECLARE zuora_account_status VARCHAR(50) DEFAULT null; 
    DECLARE zuora_account_last_invoice_date DATETIME DEFAULT null; 
    DECLARE has_active_subscriptions BOOLEAN DEFAULT false; 

    DECLARE cloud_accounts_cursor CURSOR FOR 
     SELECT 
      (SELECT `sf`.`Contact`.`CompanyName__c` FROM `sf`.`Contact` WHERE `sf`.`Asset`.`ContactId`=`sf`.`Contact`.`Id`) AS `company`, 
      `sf`.`License_Key_Association__c`.`License_Key_Status__c` AS `license_status`, 
      `sf`.`License_Key_Association__c`.`License_Key__c` AS `license_id`, 
      `sf`.`Asset`.`ContactEmail__c` AS `cloud_owner_email`, 
      (SELECT `sf`.`Contact`.`CloudEntitlementPlan__c` FROM `sf`.`Contact` WHERE `sf`.`Asset`.`ContactId`=`sf`.`Contact`.`Id`) AS `entitlement_plan`, 
      `sf`.`License_Key_Association__c`.`Role__c` AS `role`, 
      IF((SELECT `sf`.`Product2`.`IsCommercial__c` FROM `sf`.`Product2` WHERE `sf`.`Product2`.`Id`=`sf`.`Asset`.`Product2Id`) = 0,true,false) AS `is_trial`, 
      (SELECT 
       CONCAT('{""',sf.Asset_Attribute__c.Type__c,'"": {',GROUP_CONCAT(
       '""',sf.Asset_Attribute__c.Key__c,'"":""',LOWER(sf.Asset_Attribute__c.Value__c),'""' 
       ),'}}') 
       FROM 
        sf.Asset_Attribute__c 
       WHERE 
        sf.Asset_Attribute__c.Asset__c = license_id 
       GROUP BY sf.Asset_Attribute__c.Asset__c) AS `license_attributes` 
     FROM 
      `sf`.`License_Key_Association__c` 
     LEFT JOIN `sf`.`Asset` 
      ON `sf`.`License_Key_Association__c`.`License_Key__c` = `sf`.`Asset`.`Id` 
     JOIN `sf`.`Contact` 
      ON `sf`.`Contact`.`Id` = `sf`.`License_Key_Association__c`.`Contact__c` 
     WHERE 
      `sf`.`Contact`.`ExternalID__c`='someexternalidhere'; 

    DECLARE CONTINUE HANDLER FOR NOT FOUND SET no_more_cloud_accounts_records = true; 
     SELECT 
      (SELECT `sf`.`Contact`.`CompanyName__c` FROM `sf`.`Contact` WHERE `sf`.`Asset`.`ContactId`=`sf`.`Contact`.`Id`) AS `company`, 
      `sf`.`License_Key_Association__c`.`License_Key_Status__c` AS `license_status`, 
      `sf`.`License_Key_Association__c`.`License_Key__c` AS `license_id`, 
      `sf`.`Asset`.`ContactEmail__c` AS `cloud_owner_email`, 
      (SELECT `sf`.`Contact`.`CloudEntitlementPlan__c` FROM `sf`.`Contact` WHERE `sf`.`Asset`.`ContactId`=`sf`.`Contact`.`Id`) AS `entitlement_plan`, 
      `sf`.`License_Key_Association__c`.`Role__c` AS `role`, 
      IF((SELECT `sf`.`Product2`.`IsCommercial__c` FROM `sf`.`Product2` WHERE `sf`.`Product2`.`Id`=`sf`.`Asset`.`Product2Id`) = 0,true,false) AS `is_trial`, 
      (SELECT 
       CONCAT('{""',sf.Asset_Attribute__c.Type__c,'"": {',GROUP_CONCAT(
       '""',sf.Asset_Attribute__c.Key__c,'"":""',LOWER(sf.Asset_Attribute__c.Value__c),'""' 
       ),'}}') 
       FROM 
        sf.Asset_Attribute__c 
       WHERE 
        sf.Asset_Attribute__c.Asset__c = license_id 
       GROUP BY sf.Asset_Attribute__c.Asset__c) AS `license_attributes` 
     FROM 
      `sf`.`License_Key_Association__c` 
     LEFT JOIN `sf`.`Asset` 
      ON `sf`.`License_Key_Association__c`.`License_Key__c` = `sf`.`Asset`.`Id` 
     JOIN `sf`.`Contact` 
      ON `sf`.`Contact`.`Id` = `sf`.`License_Key_Association__c`.`Contact__c` 
     WHERE 
      `sf`.`Contact`.`ExternalID__c`[email protected]_externalId; 

    OPEN cloud_accounts_cursor; 
    CLOUDACCOUNTSLOOP: loop 

     fetch cloud_accounts_cursor into company, license_status, license_id, cloud_owner_email, entitlement_plan, role, is_trial, license_attributes; 

     IF is_trial = true THEN 
      SET has_active_subscriptions = true; 
     END IF; 

     SET zuora_account_id = `z`.`getZAccountId`(cloud_owner_email); 

     IF zuora_account_id IS NOT NULL THEN 
      SELECT `accountNumber`,`status`,`lastInvoiceDate` INTO zuora_account_number,zuora_account_status,zuora_account_last_invoice_date FROM zuora.Account WHERE id=zuora_account_id; 

      IF has_active_subscriptions = false THEN 
       SET has_active_subscriptions = (SELECT IF((SELECT COUNT(*) FROM `z`.`RatePlan` 
        RIGHT JOIN `z`.`ProductRatePlan` ON `z`.`RatePlan`.`productRatePlanId` = `z`.`ProductRatePlan`.`id` 
        LEFT JOIN `z`.`Subscription` ON `z`.`RatePlan`.`subscriptionId` = `z`.`Subscription`.`id` 
        WHERE 
        `z`.`ProductRatePlan`.`wowzaRatePlanCode__c` IN ((SELECT `code` FROM `z`.`zCloudRatePlanCodes`)) 
        AND `z`.`Subscription`.`status` = 'Active' 
        AND `z`.`Subscription`.`accountId` = zuora_account_id) > 0, true, false)); 
      END IF; 
     END IF; 

     REPLACE INTO `sf`.`zCloudAccounts` (`user_email`,`company`,`license_status`,`license_id`,`cloud_owner_email`,`entitlement_plan`,`role`,`is_trial`,`attributes`,`zuora_account_id`,`zuora_account_number`,`zuora_account_status`,`zuora_account_last_invoice_date`,`has_active_subscriptions`) VALUES(@p_userEmail,company,license_status,license_id,cloud_owner_email,entitlement_plan,role,is_trial,license_attributes,zuora_account_id,zuora_account_number,zuora_account_status,zuora_account_last_invoice_date,has_active_subscriptions); 

     IF no_more_cloud_accounts_records THEN 
      CLOSE cloud_accounts_cursor; 
      LEAVE CLOUDACCOUNTSLOOP; 
     end if; 

    END LOOP CLOUDACCOUNTSLOOP; 

END GETCLOUDACCOUNTS;

如果我执行GETCLOUDACCOUNTS块之外的全部选择stateout，我得到的结果我想到：

company, license_status, license_id, cloud_owner_email, entitlement_plan, role, is_trial, license_attributes 
Test Company, Active, 02iq0000000jKgMAAU, [email protected], Standard, Owner, 0, {""cloud"": {""cloud_num_247_t_streams"":""0"",""cloud_num_247_p_streams"":""0""}} 
Test Company, Active, 02iq0000000xlBBAAY, [email protected], Standard, Admin;wcl_admin;wcl_support, 0, {""cloud"": {""cloud_num_247_t_streams"":""1"",""cloud_num_247_p_streams"":""1"",""test_attribute"":""true"",""api_access"":""true""}}

但块显示license_attributes内的结果为空：

company, license_status, license_id, cloud_owner_email, entitlement_plan, role, is_trial, license_attributes 
Test Company, Active, 02iq0000000jKgMAAU, [email protected], Standard, Owner, 0, null 
Test Company, Active, 02iq0000000xlBBAAY, [email protected], Standard, Admin;wcl_admin;wcl_support, 0, null

任何帮助非常感谢！

来源

2016-06-28 kambythet

我怀疑问题是与程序变量license_id有关。

在SELECT列表中的关联的子查询包括

WHERE sf.Asset_Attribute__c.Asset__c = license_id 
             ^^^^^^^^^^

局部变量优先于列引用。由于license_id被声明为码块内的变量，

DECLARE license_id VARCHAR(18) DEFAULT null;

在SELECT语句的引用license_id是这一程序变量的引用。

在代码块之外，可能不存在名为license_id的局部变量。因此，引用license_id的相同SQL SELECT语句不是对变量的引用，而是对列的引用。

我没有查到所有的逻辑，或license_id变量的内容。但我怀疑这解释了在语句中观察到的行为差异，在代码块内部与块外执行。

来源

2016-06-28 18:07:53 spencer7593

果然！谢谢。将其更改为引用'sf'.'License_Key_Association__c'.'License_Key__c'而不是license_id变量，并且瞧！ – kambythet

我不知道为什么这个问题收到了downvote。我不认为这是一个坏问题。我提出这个问题（+10）并不是因为这是一个很好的问题，而是为了平衡不合适的downvote。 – spencer7593

谢谢。我也不确定为什么它被低估了。我认为我符合有效问题的所有标准。 – kambythet

-2

可以COALESCE照顾NULL值的你GROUP_CONCAT

COALESCE(`YourColumnName`,'')

你也可以使用一个显著不同的字符串向您展示NULL值是从哪里来的，这样你就可以修复查询。

COALESCE(`YourColumnName`,'**UNEXPECTED NULL**')

来源

2016-06-28 16:56:51

mysql存储过程group_concat在游标中选择返回null

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