游标使用示例：将zhangsan用户的创建时间更新成当前时间。

DO
BEGIN
    DECLARE CURSOR M_CURR FOR
        SELECT ID FROM USER WHERE NAME = 'zhangsan';
    DECLARE CUR_TIME TIMESTAMP;
    SELECT CURRENT_TIMESTAMP INTO CUR_TIME FROM dummy;
    FOR M_CURR_ROW AS M_CURR DO
        UPDATE USER SET CREATE_TIME = CUR_TIME
               WHERE ID = M_CURR_ROW.ID;
    END FOR;
END