为什么这个mysql函数返回null

Question

DELIMITER $$

USE `healthsystem`$$

DROP FUNCTION IF EXISTS `GetBillingProviderInfo`$$

CREATE DEFINER=`root`@`localhost` FUNCTION `GetBillingProviderInfo`(claimID LONG, claimInsCode VARCHAR(50)) RETURNS CHAR(50) DETERMINISTIC
BEGIN
    DECLARE varReturnValue                      VARCHAR(5000);
    DECLARE varProviderCode                     VARCHAR(20);
    DECLARE varLocationCode                     VARCHAR(20);
    DECLARE varFindCase                     VARCHAR(10);
    DECLARE varbillwithNPI                              VARCHAR(2);    
    DECLARE varoverrideGroupNPI                         BIT(1);        
    DECLARE varoverrideGroupNPIValue                    VARCHAR(30);   
    DECLARE varbillwithSSN                              VARCHAR(20);   
    DECLARE varoverrideTaxID                            BIT(1);        
    DECLARE varoverrideTaxIDValue                       VARCHAR(30);   
    DECLARE varoverrideName                             BIT(1);        
    DECLARE varoverrideBillingNameValue                 VARCHAR(50);  
    DECLARE varoverrideBillingAddress                   BIT(1);        
    DECLARE varoverrideAddress1                         VARCHAR(255);  
    DECLARE varoverrideAddress2                         VARCHAR(255);  
    DECLARE varoverrideCity                             VARCHAR(255);  
    DECLARE varoverrideState                            VARCHAR(2);    
    DECLARE varoverrideZipCode                          VARCHAR(20);   
    DECLARE varBoxNo33BillingName                   VARCHAR(50);
    DECLARE varBoxNo33Address1                  VARCHAR(50);
    DECLARE varBoxNo33Address2                  VARCHAR(50);
    DECLARE varBoxNo33City                      VARCHAR(20);
    DECLARE varBoxNo33State                     VARCHAR(2);
    DECLARE varBoxNo33ZipCode                   VARCHAR(10);
    DECLARE varLastName                     VARCHAR(100);
    DECLARE varFirstName                        VARCHAR(100);
    DECLARE varMiddleName                       VARCHAR(100);
    DECLARE varPracticeID                       BIGINT;
    DECLARE varrecordCount                      INT;
    RETURN  varReturnValue;



     RETURN CONCAT('Hello, ',s,'!');


    END$$

DELIMITER ;

SELECT GetBillingProviderInfo(51,'MEDICARE-GHI');

Answer 1

由于：

RETURN  varReturnValue;

您以后的RETURN CONCAT('Hello, ',s,'!')无法执行。