触发器附近信号语句中的 concat 语法错误

Question

请帮助我了解 MySQL 5.6 的语法。

出于某种原因，我收到错误消息：

ERROR 1064 (42000): You have an error in your SQL syntax; 
check the manual that corresponds to your MySQL server version 
for the right syntax to use near '('WRONG SOCIAL: ', new.social);
        end if;
        if not (new.photo is nul'

尝试运行此 SQL 代码时：

create table table_social (
        sid varchar(250) primary key,
        auth char(32) not null,
        social integer,               -- to be checked by triggers
        female boolean,
        given varchar(250) not null,
        family varchar(250) null,
        photo varchar(1000) null,     -- to be checked by triggers
        place varchar(250) null,
        ip varchar(250) not null,
        uid integer not null references 
            table_users(uid) on delete cascade
);

delimiter //

create trigger social_insert_trigger before insert on table_social
for each row begin
        if new.social < 0 OR new.social > 6 then
                signal sqlstate '45000' 
                set message_text = concat('WRONG SOCIAL: ', new.social);
        end if;
        if not (new.photo is null OR new.photo regexp '^https?://') then
                signal sqlstate '45000' 
                set message_text = concat('WRONG PHOTO: ', new.photo);
        end if;
end
//

create trigger social_update_trigger before update on table_social
for each row begin
        if new.social < 0 OR new.social > 6 then
                signal sqlstate '45000' 
                set message_text = concat('WRONG SOCIAL: ', new.social);
        end if;
        if not (new.photo is null OR new.photo regexp '^https?://') then
                signal sqlstate '45000' 
                set message_text = concat('WRONG PHOTO: ', new.photo);
        end if;
end
//

我尝试删除concat，用双引号替换单引号，将signal行一分为二（如上）并返回 - 但仍然找不到，出了什么问题。

Answer 1

测试这段代码：

drop table if EXISTS table_social;
create table table_social (
        sid varchar(250) primary key,
        auth char(32) not null,
        social integer,               -- to be checked by triggers
        female boolean,
        given varchar(250) not null,
        family varchar(250) null,
        photo varchar(1000) null,     -- to be checked by triggers
        place varchar(250) null,
        ip varchar(250) not null,
        uid integer not null references 
            table_users(uid) on delete cascade
);

delimiter //

create trigger social_insert_trigger before insert on table_social
for each row begin
        if new.social < 0 OR new.social > 6 then
                set @message_text = concat('WRONG SOCIAL: ', new.social);
                signal sqlstate '45000'
                set MESSAGE_TEXT = @message_text;
        end if;
        if not (new.photo is null OR new.photo regexp '^https?://') then
                set @message_text = concat('WRONG PHOTO: ', new.photo);
                signal sqlstate '45000' set message_text = @message_text;
        end if;
end
//

create trigger social_update_trigger before update on table_social
for each row begin
        if new.social < 0 OR new.social > 6 then
                set @message_text = concat('WRONG SOCIAL: ', new.social);
                signal sqlstate '45000' 
                set message_text = @message_text;
        end if;
        if not (new.photo is null OR new.photo regexp '^https?://') then
                set @message_text = concat('WRONG PHOTO: ', new.photo);
                signal sqlstate '45000' 
                set message_text = @message_text;
        end if;
end
//

它不明白CONCAT（）在SIGNAL SQLSTATE SET MESSAGE_TEXT