創建MySQL功能

Question

我想創建與下面的查詢功能，但是發生錯誤

DELIMITER $$ 
CREATE FUNCTION getOnlineUserTraffic (x1 VARCHAR(32)) 
RETURNS FLOAT 
DETERMINISTIC 
BEGIN 
    DECLARE dist FLOAT; 
    SET dist = SELECT UsedCreditTraffic FROM uonlineuser WHERE UserName=x1 
    RETURN dist; 
END$$ 
DELIMITER ; 

//的userName =與長度焦炭= 32

// UsedCreditTraffic =浮

Answer 1

嘗試：

DELIMITER $$ 

DROP FUNCTION IF EXISTS getOnlineUserTraffic$$ 

CREATE FUNCTION getOnlineUserTraffic(x1 VARCHAR(32)) 
RETURNS FLOAT 
DETERMINISTIC 
BEGIN 
    DECLARE dist FLOAT; 
    SET dist = (SELECT UsedCreditTraffic FROM uonlineuser WHERE UserName=x1); 
    RETURN dist; 
END$$ 

DELIMITER ; 

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