Select查询返回存储过程内的多个值

Question

我已经创建了用于创建测试数据的存储过程：

create procedure INSERT_INTO_VALIDATEEXISTINGYESID(IN customerid varchar(50), IN dgaccounttype varchar(50),
                                                   IN scenario varchar(1000), IN yesid varchar(50),
                                                   IN accountnumber varchar(50), IN accounttype varchar(30),
                                                   IN billingaccountnumber varchar(50), IN valid varchar(10),
                                                   IN responsecode varchar(20))
BEGIN

  DECLARE `l_customerid` VARCHAR(50);
  DECLARE `l_dgaccounttype` VARCHAR(50);
  DECLARE `l_scenario` VARCHAR(1000);
  DECLARE `l_yesid` VARCHAR(50);
  DECLARE `l_accountnumber` VARCHAR(50);
  DECLARE `l_accounttype` VARCHAR(30);
  DECLARE `l_billingaccountnumber` VARCHAR(50);
  DECLARE `l_valid` VARCHAR(50);
  DECLARE `l_responsecode` VARCHAR(50);


  SET l_customerid = customerid;

  SET l_dgaccounttype = dgaccounttype;

  IF (scenario IS NOT NULL) THEN
    SET l_scenario = scenario;
  ELSE
    SET l_scenario = NULL;
  END IF;

  IF (yesid IS NOT NULL) THEN
    IF (yesid = '<service_auto>') THEN
      SET l_yesid = (SELECT serviceaccountyesid
                     FROM createcustomer
                     WHERE customerid = l_customerid
                       AND dgaccounttype = l_dgaccounttype);
    ELSEIF (yesid = '<customer_auto>') THEN
      SET l_yesid = (SELECT `customeraccountyesid`
                     FROM createcustomer
                     WHERE customerid = l_customerid
                       AND dgaccounttype = l_dgaccounttype);
    ELSE
      SET l_yesid = yesid;
    END IF;
  ELSE
    SET l_yesid = '';
  END IF;

  IF (accountnumber IS NOT NULL) THEN
    IF (accountnumber = '<service_auto>') THEN
      SET l_accountnumber = (SELECT `serviceaccountnumber`
                             FROM createcustomer
                             WHERE customerid = l_customerid
                               AND dgaccounttype = l_dgaccounttype);
    ELSEIF (accountnumber = '<customer_auto>') THEN
      SET l_accountnumber = (SELECT `customeraccountnumber`
                             FROM createcustomer
                             WHERE customerid = l_customerid
                               AND dgaccounttype = l_dgaccounttype);
      INSERT INTO debug(valueobj) VALUES (l_accountnumber);
    ELSEIF (accountnumber = '<billing_auto>') THEN
      SET l_accountnumber = (SELECT `billingaccountnumber`
                             FROM createcustomer
                             WHERE customerid = l_customerid
                               AND dgaccounttype = l_dgaccounttype);
    ELSE
      SET l_accountnumber = accountnumber;
    END IF;
  ELSE
    SET l_accountnumber = '';
  END IF;

  insert into debug(valueobj) values (l_accountnumber);

  IF (accounttype = '<auto>') THEN
    SET l_accounttype =
        (SELECT `accounttype`
         FROM createcustomer
         WHERE customerid = l_customerid
           AND dgaccounttype = l_dgaccounttype
         LIMIT 1);
  ELSE
    SET l_accounttype = accounttype;
  END IF;

  insert into debug(valueobj) values (accounttype);

  IF (billingaccountnumber = '<auto>') THEN
    SET l_billingaccountnumber = (SELECT billingaccountnumber
                                  FROM createcustomer
                                  WHERE customerid = l_customerid
                                    AND dgaccounttype = l_dgaccounttype);
  ELSE
    SET l_billingaccountnumber = billingaccountnumber;
  END IF;


  SET l_responsecode = responsecode;


  SET l_valid = valid;


  INSERT INTO `validateexistingyesid`(customerid, dgaccounttype, scenario, yesid, `accountnumber`, `accounttype`,
                                      `billingaccountnumber`, valid, responsecode, createddate)
  VALUES (l_customerid, l_dgaccounttype, l_scenario, l_yesid, l_accountnumber, l_accounttype,
          l_billingaccountnumber, l_valid, l_responsecode, NOW());

END;

但是当我执行上述过程时，出现以下错误：

[21000][1242] Subquery returns more than 1 row

我已经检查了过程中的每个选择，并且它仅返回一个值。但是在存储过程中，它返回多个值。 EQUALS的行为类似于LIKE。

请帮助。