触发器声明中的局部变量中的语法错误

Question

我有以下存储过程

CREATE PROCEDURE `update_ordenes`()
BEGIN
    DECLARE record CURSOR FOR 
        SELECT ordenes.idorden, ordenes.idafiliado 
            FROM ordenes, afiliados 
            WHERE afiliados.idafiliado = ordenes.idafiliado;

    OPEN record;
    REPEAT
        FETCH record INTO @id_orden, @id_afil_viejo;

        INSERT INTO afil2(nombre, apellido, documento) 
            (SELECT nombre, apellido, documento
                FROM afiliados 
                WHERE idafiliado = @id_afil_viejo);

        SET @last_id = (SELECT id FROM afil2 ORDER BY id DESC LIMIT 1);

        UPDATE ordenes 
        SET afil2 = @last_id,
            ordenes.idafiliado = NULL
        WHERE ordenes.idafiliado = @id_afil_viejo
              AND ordenes.idorden = @orden_id;
    UNTIL done END REPEAT;
END

由于某种原因，我在FETCH record INTO @id_orden, @id_afil_viejo; 行收到语法错误

在mysql documentation 中我可以运行SELECT id, data INTO @x, @y FROM test.t1 LIMIT 1;。 是FETCH的使用有问题吗？或者有什么问题？

Answer 1

FETCH（从游标中获取下一条记录并前进）与SELECT ... INTO（仅适用于返回单个记录的查询）不相同。 p>

FETCH 可以仅获取到local variables（没有@ 前缀，但必须在存储程序的开头为DECLAREd），而SELECT ... INTO 也可以获取到user-defined variables（确实有@前缀并且不是DECLAREd）。

因此，您必须 DECLARE 一个局部变量，您的记录将在其中 FETCHed：

CREATE PROCEDURE `update_ordenes`()
BEGIN

    DECLARE id_orden BIGINT UNSIGNED DEFAULT 5;  -- as appropriate
    DECLARE id_afiv_viejo VARCHAR(15) NOT NULL;  -- as appropriate

    DECLARE record CURSOR FOR 
        SELECT ordenes.idorden, ordenes.idafiliado 
            FROM ordenes, afiliados 
            WHERE afiliados.idafiliado = ordenes.idafiliado;

    OPEN record;
    REPEAT
        FETCH record INTO id_orden, id_afil_viejo;

        INSERT INTO afil2(nombre, apellido, documento) 
            (SELECT nombre, apellido, documento
                FROM afiliados 
                WHERE idafiliado = id_afil_viejo);

        SET @last_id = (SELECT id FROM afil2 ORDER BY id DESC LIMIT 1);

        UPDATE ordenes 
        SET afil2 = @last_id,
            ordenes.idafiliado = NULL
        WHERE ordenes.idafiliado = id_afil_viejo
              AND ordenes.idorden = id_orden;
    UNTIL done END REPEAT;
END

总而言之，您的存储过程非常不安全（在第一个 INSERT 语句和随后的 SET 之间存在竞争危险），并且执行本应更简单的事情的方法非常笨拙。