mysql触发器

/*
 * 添加数据之后报名人数加一
 */
DELIMITER $$
CREATE TRIGGER trigger_insert_enrolment_party_info
    AFTER INSERT ON `enrolment`
    FOR EACH ROW
    BEGIN
        UPDATE party_info SET signin_num=signin_num+1 WHERE id=new.party_id;
    END$$
    
/**
 * 删除数据之后报名人数减一
 */
DELIMITER $$
CREATE TRIGGER trigger_delete_enrolment_party_info
    AFTER DELETE ON `enrolment`
    FOR EACH ROW
    BEGIN
        UPDATE `party_info` SET signin_num = signin_num-1 WHERE id = old.party_id AND signin_num > 0;
    END$$
    
/**
 * 修改报名状态：1、由待审核变成未通过(报名数量减一)，2、未通过变成待审核(报名数量加一)
 */
DELIMITER $$
CREATE TRIGGER trigger_update_enrolment_party_info
    AFTER UPDATE ON `enrolment`
    FOR EACH ROW
    BEGIN
        IF old.status = 'unaudited' AND new.status = 'notpass'
            THEN  SET @signin_num = signin_num-1;
        ELSEIF (old.status = 'notpass' AND new.status = 'unaudited') OR (old.status = 'quit' AND new.status = 'unaudited')
            THEN SET @signin_num = signin_num+1;
        END IF;
        UPDATE party_info SET signin_num = @signin_num WHERE id = new.party_id;
    END$$