问个初级问题 mysql触发器更新表是怎么写的?比如A表的a1字段更新时,b表的b1字段同时也跟着更新,a表和b表通过a2,b2字段关联 解决方案 » 免费领取超大流量手机卡,每月29元包185G流量+100分钟通话, 中国电信官方发货 为什么不看帮助中的例子?以下摘自 MySQL 5.1 Reference ManualCREATE TABLE test1(a1 INT);CREATE TABLE test2(a2 INT);CREATE TABLE test3(a3 INT NOT NULL AUTO_INCREMENT PRIMARY KEY);CREATE TABLE test4( a4 INT NOT NULL AUTO_INCREMENT PRIMARY KEY, b4 INT DEFAULT 0);DELIMITER |CREATE TRIGGER testref BEFORE INSERT ON test1 FOR EACH ROW BEGIN INSERT INTO test2 SET a2 = NEW.a1; DELETE FROM test3 WHERE a3 = NEW.a1; UPDATE test4 SET b4 = b4 + 1 WHERE a4 = NEW.a1; END;|DELIMITER ;INSERT INTO test3 (a3) VALUES (NULL), (NULL), (NULL), (NULL), (NULL), (NULL), (NULL), (NULL), (NULL), (NULL);INSERT INTO test4 (a4) VALUES (0), (0), (0), (0), (0), (0), (0), (0), (0), (0);Suppose that you insert the following values into table test1 as shown here: mysql> INSERT INTO test1 VALUES -> (1), (3), (1), (7), (1), (8), (4), (4);Query OK, 8 rows affected (0.01 sec)Records: 8 Duplicates: 0 Warnings: 0As a result, the data in the four tables will be as follows: mysql> SELECT * FROM test1;+------+| a1 |+------+| 1 || 3 || 1 || 7 || 1 || 8 || 4 || 4 |+------+8 rows in set (0.00 sec)mysql> SELECT * FROM test2;+------+| a2 |+------+| 1 || 3 || 1 || 7 || 1 || 8 || 4 || 4 |+------+8 rows in set (0.00 sec)mysql> SELECT * FROM test3;+----+| a3 |+----+| 2 || 5 || 6 || 9 || 10 |+----+5 rows in set (0.00 sec)mysql> SELECT * FROM test4;+----+------+| a4 | b4 |+----+------+| 1 | 3 || 2 | 0 || 3 | 1 || 4 | 2 || 5 | 0 || 6 | 0 || 7 | 1 || 8 | 1 || 9 | 0 || 10 | 0 |+----+------+10 rows in set (0.00 sec). [align=center]==== 思想重于技巧 ====[/align].贴子分数<20:对自已的问题不予重视。贴子大量未结:对别人的回答不予尊重。. reply via CSDN viewer 推荐你看一下这些帮助SQL 1992MySQL 5.1 Reference ManualActiveX Data Objects 2.5 Reference 下载数据库系统概论PPT. [align=center]==== 思想重于技巧 ====[/align].贴子分数<20:对自已的问题不予重视。贴子大量未结:对别人的回答不予尊重。. reply via CSDN viewer 如何在C#中创建并使用MySql数据库 mysql的select效率太慢怎么优化? 如何进行 MYSQL 监控(性能,查询状态)----分不多,求指导 mysql配置JDO的问题 load data local infile 插不进去 mysql怎么限制数据库大小? 一個急切而又簡單的問題,在MYSQL數据庫中,要輸入中文字,怎么辦 mysql 一个查询语句,初学者,不会,请大家包含. 怎么打开扩展名为.frm的文件?谢谢! MySql 中的触发器 问个初级问题 请问下什么语句能重新刷新索引,并且不是每次执行操作后都更新索引呢?谢谢
CREATE TABLE test1(a1 INT);
CREATE TABLE test2(a2 INT);
CREATE TABLE test3(a3 INT NOT NULL AUTO_INCREMENT PRIMARY KEY);
CREATE TABLE test4(
a4 INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
b4 INT DEFAULT 0
);DELIMITER |CREATE TRIGGER testref BEFORE INSERT ON test1
FOR EACH ROW BEGIN
INSERT INTO test2 SET a2 = NEW.a1;
DELETE FROM test3 WHERE a3 = NEW.a1;
UPDATE test4 SET b4 = b4 + 1 WHERE a4 = NEW.a1;
END;
|DELIMITER ;INSERT INTO test3 (a3) VALUES
(NULL), (NULL), (NULL), (NULL), (NULL),
(NULL), (NULL), (NULL), (NULL), (NULL);INSERT INTO test4 (a4) VALUES
(0), (0), (0), (0), (0), (0), (0), (0), (0), (0);Suppose that you insert the following values into table test1 as shown here: mysql> INSERT INTO test1 VALUES
-> (1), (3), (1), (7), (1), (8), (4), (4);
Query OK, 8 rows affected (0.01 sec)
Records: 8 Duplicates: 0 Warnings: 0As a result, the data in the four tables will be as follows: mysql> SELECT * FROM test1;
+------+
| a1 |
+------+
| 1 |
| 3 |
| 1 |
| 7 |
| 1 |
| 8 |
| 4 |
| 4 |
+------+
8 rows in set (0.00 sec)mysql> SELECT * FROM test2;
+------+
| a2 |
+------+
| 1 |
| 3 |
| 1 |
| 7 |
| 1 |
| 8 |
| 4 |
| 4 |
+------+
8 rows in set (0.00 sec)mysql> SELECT * FROM test3;
+----+
| a3 |
+----+
| 2 |
| 5 |
| 6 |
| 9 |
| 10 |
+----+
5 rows in set (0.00 sec)mysql> SELECT * FROM test4;
+----+------+
| a4 | b4 |
+----+------+
| 1 | 3 |
| 2 | 0 |
| 3 | 1 |
| 4 | 2 |
| 5 | 0 |
| 6 | 0 |
| 7 | 1 |
| 8 | 1 |
| 9 | 0 |
| 10 | 0 |
+----+------+
10 rows in set (0.00 sec).
[align=center]==== 思想重于技巧 ====
[/align]
.
贴子分数<20:对自已的问题不予重视。
贴子大量未结:对别人的回答不予尊重。
.
SQL 1992
MySQL 5.1 Reference Manual
ActiveX Data Objects 2.5 Reference 下载
数据库系统概论PPT.
[align=center]==== 思想重于技巧 ====
[/align]
.
贴子分数<20:对自已的问题不予重视。
贴子大量未结:对别人的回答不予尊重。
.