MySQL - Syntax Error in Stored Procedure using `if`

问题

I need to know what is the error in the following stored procedure, as begging with mySql I can't understand what is the error

if not EXISTS( select filesrefrences.ReferenceID  from filesrefrences where filesrefrences.RefrenceKey= pRefrenceKey)
BEGIN
        Insert into filesrefrences                      
                            (                   
                                    filesrefrences.RefrenceKey,
                                    filesrefrences.RefrenceCount
                            )
                        VALUES
                         (                      
                                    pRefrenceKey,
                                    1
                         );
        select LAST_INSERT_ID();
        END
ELSE
BEGIN
        UPDATE filesrefrences
        set filesrefrences.RefrenceCount= filesrefrences.RefrenceCount+1
        WHERE filesrefrences.ReferenceID= ExistedReferenceID;
        SELECT ExistedReferenceID;
    END

it gives error in line no# 4

回答1:

You have not used THEN keyword and END IF.

Try this:

SET @ExistedRefID = NULL;
SELECT ReferenceID INTO @ExistedRefID 
FROM filesrefrences 
WHERE RefrenceKey= pRefrenceKey;

IF (@ExistedRefID IS NULL) THEN 
    INSERT INTO filesrefrences(RefrenceKey, RefrenceCount)
    VALUES(pRefrenceKey,1);
    SELECT LAST_INSERT_ID();
ELSE
    UPDATE filesrefrences
    SET RefrenceCount= RefrenceCount+1
    WHERE ReferenceID= @ExistedRefID;
    SELECT @ExistedRefID;
END IF;

来源：https://stackoverflow.com/questions/14134105/mysql-syntax-error-in-stored-procedure-using-if