MySql错误：无法更新存储的函数/触发器中的表，因为它已被调用此存储函数/触发器的语句使用

Question

我正在运行MySQL查询。但是，当一个新的行从表单输入添加我得到这个错误：

Error: Can't update table 'brandnames' in stored function/trigger because it is 
already used by statement which invoked this stored function/trigger. 

从代码：

CREATE TRIGGER `capital` AFTER INSERT ON `brandnames` 
FOR EACH 
ROW UPDATE brandnames 
SET bname = CONCAT(UCASE(LEFT(bname, 1)) , LCASE(SUBSTRING(bname, 2))) 

这个错误是什么意思？

Answer 1

而INSERT触发器被解雇你不能改变一个表。 INSERT可能会执行一些可能导致死锁的锁定。另外，从触发器更新表格会导致同一个触发器在无限递归循环中再次触发。这些原因都是MySQL阻止你这样做的原因。

但是，根据您要实现的内容，您可以使用NEW.fieldname或旧值（如果使用OLD进行UPDATE）访问新值。

如果你有一排名为full_brand_name，你想用前两个字母作为一个简短的名字在外地small_name您可以使用：

CREATE TRIGGER `capital` BEFORE INSERT ON `brandnames` 
FOR EACH ROW BEGIN 
    SET NEW.short_name = CONCAT(UCASE(LEFT(NEW.full_name,1)) , LCASE(SUBSTRING(NEW.full_name,2))) 
END 

Answer 2

正确的语法是：

FOR EACH ROW SET NEW.bname = CONCAT(UCASE(LEFT(NEW.bname, 1)) 
            , LCASE(SUBSTRING(NEW.bname, 2))) 

Answer 3

我有同样的问题并解决添加“新“。在更新字段之前。我在这里发表充满触发有人想写一个触发器

DELIMITER $$ 

USE `nc`$$ 

CREATE 
    TRIGGER `nhachung_province_count_update` BEFORE UPDATE ON `nhachung` 
    FOR EACH ROW BEGIN 

    DECLARE slug_province VARCHAR(128); 
    DECLARE slug_district VARCHAR(128); 

    IF old.status!=new.status THEN /* neu doi status */ 
     IF new.status="Y" THEN 
      UPDATE province SET `count`=`count`+1 WHERE id = new.district_id; 
     ELSE 
      UPDATE province SET `count`=`count`-1 WHERE id = new.district_id; 
     END IF; 
    ELSEIF old.province_id!=new.province_id THEN /* neu doi province_id + district_id */ 

     UPDATE province SET `count`=`count`+1 WHERE id = new.province_id; /* province_id */ 
     UPDATE province SET `count`=`count`-1 WHERE id = old.province_id; 
     UPDATE province SET `count`=`count`+1 WHERE id = new.district_id; /* district_id */ 
     UPDATE province SET `count`=`count`-1 WHERE id = old.district_id; 

     SET slug_province = (SELECT slug FROM province WHERE id= new.province_id LIMIT 0,1); 
     SET slug_district = (SELECT slug FROM province WHERE id= new.district_id LIMIT 0,1); 
     SET new.prov_dist_url=CONCAT(slug_province, "/", slug_district); 

    ELSEIF old.district_id!=new.district_id THEN 

     UPDATE province SET `count`=`count`+1 WHERE id = new.district_id; 
     UPDATE province SET `count`=`count`-1 WHERE id = old.district_id; 

     SET slug_province = (SELECT slug FROM province WHERE id= new.province_id LIMIT 0,1); 
     SET slug_district = (SELECT slug FROM province WHERE id= new.district_id LIMIT 0,1); 
     SET new.prov_dist_url=CONCAT(slug_province, "/", slug_district); 

    END IF; 


    END; 
$$ 

DELIMITER ; 

希望这有助于有人

Answer 4

A“之前，插入” - 触发器是实现对插入相同的表更新的唯一途径，并且只能从MySQL 5.5+开始。但是，自动增量字段的值仅适用于“AFTER-INSERT”触发器 - 它在BEFORE-case中默认为0。因此下面的示例代码将设置基础上，自动递增值id将编译一个预先计算的代理键的值，但实际并不起作用，因为NEW.id将始终为0：

create table products(id int not null auto_increment, surrogatekey varchar(10), description text); 
create trigger trgProductSurrogatekey before insert on product 
for each row set NEW.surrogatekey = 
    (select surrogatekey from surrogatekeys where id = NEW.id);