MySQL 语法（函数）错误

Question

CREATE FUNCTION FC_IDKRITERIA()
RETURNS CHAR(3)
AS
BEGIN
DECLARE @MAX INT , @KODEBARU CHAR(3)  
SELECT @MAX = MAX (RIGHT(IDKRITERIA,2)) FROM KRITERIA
IF @MAX IS NULL 
SET @MAX = 0
SET @KODEBARU = 'K' + RIGHT('0'+CONVERT(VARCHAR(3),@MAX+ 1 ) ,2)
RETURN @KODEBARU
END

Answer 1

Every statement in a procedure must end with ; . To keep this from ending the function definition, use the DELIMITER command to change the command delimiter to something else.

And when doing a variable assignment in a SELECT clause, you have to use := .

There's no AS at the beginning of a function definition.

You don't declare variables that begin with @ .

You need THEN and END IF in an IF statement.

To concatenate strings, use CONCAT() , not + .

You have the arguments to CONVERT() in the wrong order, and VARCHAR(3) is not a valid type argument, it should be CHAR(3) .

In a function, you can't use a SELECT statement at the top-level, because that means to return the result set, and functions can only return single values. So you have to assign @MAX from a (SELECT ...) expression.

DELIMITER $$

CREATE FUNCTION FC_IDKRITERIA() RETURNS CHAR(3)
BEGIN
    SET @MAX = (SELECT MAX (RIGHT(IDKRITERIA,2)) FROM KRITERIA);
    IF @MAX IS NULL 
    THEN SET @MAX = 0;
    END IF;
    SET @KODEBARU = CONCAT('K', RIGHT('0'+CONVERT(@MAX+ 1, CHAR(3)) ,2));
    RETURN @KODEBARU;
END;
$$
DELIMITER ;