看别人的项目，就是数据库的表看不懂，帮忙解释下

Question

-- MySQL dump 10.11

-- Host: localhost Database: zxdy

---

-- Server version 5.0.41-community-nt

/*!40101 SET @OLD_CHARACTER_SET_CLIENT=@@CHARACTER_SET_CLIENT /;
/!40101 SET @OLD_CHARACTER_SET_RESULTS=@@CHARACTER_SET_RESULTS /;
/!40101 SET @OLD_COLLATION_CONNECTION=@@COLLATION_CONNECTION /;
/!40101 SET NAMES latin1 /;
/!40103 SET @OLD_TIME_ZONE=@@TIME_ZONE /;
/!40103 SET TIME_ZONE='+00:00' /;
/!40014 SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0 /;
/!40014 SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0 /;
/!40101 SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO' /;
/!40111 SET @OLD_SQL_NOTES=@@SQL_NOTES, SQL_NOTES=0 */;

-- Table structure for table dy_apply

DROP TABLE IF EXISTS dy_apply;
CREATE TABLE dy_apply (
AID int(11) NOT NULL auto_increment,
UID int(11) default NULL,
TGID int(11) default NULL,
AReason varchar(200) NOT NULL,
AFlag int(11) default '0',
AStatus char(10) default '申请中',
PRIMARY KEY (AID),
KEY UID (UID),
KEY TGID (TGID),
[color=red] CONSTRAINT dy_apply_ibfk_1 FOREIGN KEY (UID) REFERENCES dy_user (UID) ON DELETE CASCADE,
CONSTRAINT dy_apply_ibfk_2 FOREIGN KEY (TGID) REFERENCES dy_topic_group (TGID) ON DELETE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=latin1;[/color]--

-- Dumping data for table dy_apply

[color=red]LOCK TABLES dy_apply WRITE;[/color]/*!40000 ALTER TABLE dy_apply DISABLE KEYS /;
INSERT INTO dy_apply VALUES (2,1,10002,'范德萨发大萨菲',1,'拒绝申请'),(3,1,10004,'范德萨发大',0,'申请中'),(4,1,10000,'fsfaf',1,'拒绝申请'),(5,1,10002,'dsf',1,'拒绝申请'),(7,3,10002,'范德萨发大是',1,'同意申请'),(8,1,10002,'feafdsafdsafdas',1,'同意申请'),(9,1,10000,'fefewfewa',1,'同意申请'),(10,1,10003,'21',0,'申请中'),(11,1,10008,'fdsa',0,'申请中'),(12,1,10006,'想学习',0,'申请中');
/!40000 ALTER TABLE dy_apply ENABLE KEYS */;
UNLOCK TABLES;

-- Table structure for table dy_revert

DROP TABLE IF EXISTS dy_revert;
CREATE TABLE dy_revert (
RID int(11) NOT NULL auto_increment,
TID int(11) default NULL,
UID int(11) default NULL,
RTitle varchar(200) default NULL,
RContent text NOT NULL,
RDate datetime NOT NULL,
PRIMARY KEY (RID),
KEY TID (TID),
KEY UID (UID),
[color=red] CONSTRAINT dy_revert_ibfk_1 FOREIGN KEY (TID) REFERENCES dy_topic (TID) ON DELETE CASCADE,
CONSTRAINT dy_revert_ibfk_2 FOREIGN KEY (UID) REFERENCES dy_user (UID) ON DELETE CASCADE

) ENGINE=InnoDB DEFAULT CHARSET=latin1;[/color]

-- Dumping data for table dy_revert

[color=red]LOCK TABLES dy_revert WRITE;[/color]/*!40000 ALTER TABLE dy_revert DISABLE KEYS /;
INSERT INTO dy_revert VALUES (1,2,3,'','看书，上网问问题','2008-12-08 11:08:31'),(2,1,3,'','传说新版本的JAVA 会自动缓存BYTE范围内的值.','2008-12-08 11:08:31'),(3,1,3,'','楼主懂了吗？可以参考Java里的源代码','2008-12-08 11:08:31'),(4,1,3,'','谢谢大家指教','2008-12-08 11:08:31'),(5,3,3,'','认真学习，专心研究的话就好学','2008-12-08 11:08:31'),(6,10,1,'','\r\n测试测试测试测试测试测试测试测试测试10\r\n测试测试测试测试测试测试测试测试测试10\r\n测试测试测试测试测试测试测试测试测试10','2008-12-08 20:13:07'),(7,10,1,'回答 xyz 的问题','\r\n测试测试测试测试测试测试测试测试测试10\r\n测试测试测试测试测试测试测试测试测试10\r\n测试测试测试测试测试测试测试测试测试10','2008-12-08 20:13:15'),(8,1,2,'','都是一个人????','2008-12-10 23:01:33'),(9,6,2,'','新版本会缓存的 呵呵','2008-12-11 23:24:32'),(10,8,1,'','再次测试啊啊啊 啊','2008-12-12 01:16:36'),(11,10,1,'','学生\r\n\r\n注册时间 2008-12-08\r\n\r\n最后登陆 2008-12-12\r\n 2楼 发表于 2008-12-08 20:13:15 回答 xyz 的问题\r\n测试测试测试测试测试测试测试测试测试10 测试测试测试测试测试测试测试测试测试10 测试测试测试测试测试测试测试测试测试10 ','2008-12-12 01:16:56'),(12,4,2,'','回答过的问题嘛算法','2008-12-12 10:58:57'),(13,10,2,'','回答过了，是不是没有了么','2008-12-12 13:08:35'),(14,3,2,'','回答了 谢谢 呵呵。。。','2008-12-12 13:27:24'),(15,15,1,'','bbbbbbbbbbbbbbbbb','2009-03-16 20:45:19'),(16,15,1,'','ccccccccccccccc','2009-03-16 20:59:07'),(17,17,1,'','ssssssssssssssssss','2009-03-16 21:00:10');
/!40000 ALTER TABLE dy_revert ENABLE KEYS */;
UNLOCK TABLES;

-- Table structure for table dy_topic

DROP TABLE IF EXISTS dy_topic;
CREATE TABLE dy_topic (
TID int(11) NOT NULL auto_increment,
UID int(11) default NULL,
TGID int(11) default NULL,
TTitle varchar(200) NOT NULL,
TContent text NOT NULL,
TDate datetime NOT NULL,
TReadCount int(11) default '0',
PRIMARY KEY (TID),
KEY UID (UID),
KEY TGID (TGID),
CONSTRAINT dy_topic_ibfk_1 FOREIGN KEY (UID) REFERENCES dy_user (UID) ON DELETE CASCADE,
CONSTRAINT dy_topic_ibfk_2 FOREIGN KEY (TGID) REFERENCES dy_topic_group (TGID) ON DELETE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

-- Dumping data for table dy_topic

LOCK TABLES dy_topic WRITE;
/*!40000 ALTER TABLE dy_topic DISABLE KEYS /;
INSERT INTO dy_topic VALUES (1,1,10001,'怎样学习框架ssh','学习struts spring hibernate 的顺序是ssh吗 顺便根据我的情况推荐几本书','2008-12-08 11:07:16',31),(2,2,10003,'C++很难吗？应该怎么样学习呢','请给我推荐几本C++的书，给我讲些学习方法谢谢','2008-12-08 11:07:16',19),(3,2,10001,'测试','测试测试测试测试测试测试测试测试测试','2008-12-08 11:07:16',19),(4,1,10001,'JAVA很难吗？应该怎么样学习呢','请给我推荐几本JAVA的书，给我讲些学习方法谢谢','2008-12-08 11:07:16',14),(5,1,10002,'请教一句SQL这么写。。','这个SQL好难啊，应该怎么学呢','2008-12-08 11:07:16',12),(6,1,10001,'Integer类的一个小问题 ==比较','Integer内的值的大小在Byte范围内时，==比较返回true 在那范围之外返回false \n这是为什么呢，为什么会这样》？ ','2008-12-08 11:07:34',32),(7,1,10002,'测试71','测试测试测试测试测试测试测试测试测试7','2008-12-08 11:08:09',13),(8,1,10001,'测试81','测试测试测试测试测试测试测试测试测试8','2008-12-08 11:08:09',21),(9,1,10002,'测试91','测试测试测试测试测试测试测试测试测试9','2008-12-08 11:08:09',16),(10,1,10001,'测试101','测试测试测试测试测试测试测试测试测试10','2008-12-08 11:08:09',29),(11,1,10002,'测试111','测试测试测试测试测试测试测试测试测试11','2008-12-08 11:08:09',12),(12,1,10001,'测试121','测试测试测试测试测试测试测试测试测试12','2008-12-08 11:08:09',13),(13,1,10005,'自动控制的课本是哪个？','自动控制的课本是哪个？自动控制的课本是哪个？自动控制的课本是哪个？','2008-12-12 01:18:07',2),(14,1,10000,'我是第一个来到这里的','第一个提问的哦 呵呵','2008-12-12 14:01:29',1),(15,1,10000,'aaaaaaaaaa','aabbbbbbbbbbbbbbbbbbbb','2009-03-16 20:44:05',6),(16,1,10000,'bbccccccccccccc','aaaaaaaaaaaaaa','2009-03-16 20:58:57',0),(17,1,10000,'11111111111111111','22222222222222222222','2009-03-16 21:00:00',2);
/!40000 ALTER TABLE dy_topic ENABLE KEYS */;
UNLOCK TABLES;

-- Table structure for table dy_topic_group

DROP TABLE IF EXISTS dy_topic_group;
CREATE TABLE dy_topic_group (
TGID int(11) NOT NULL auto_increment,
TGName varchar(50) NOT NULL,
TDetail varchar(200) NOT NULL,
PRIMARY KEY (TGID)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

-- Dumping data for table dy_topic_group

LOCK TABLES dy_topic_group WRITE;
/*!40000 ALTER TABLE dy_topic_group DISABLE KEYS /;
INSERT INTO dy_topic_group VALUES (10000,'Java网络编程','计算机与自动控制学院'),(10001,'数据库系统概论','计算机与自动控制学院'),(10002,'C语言程序设计','计算机与自动控制学院'),(10003,'高等数学','理学院'),(10004,'线性代数','理学院'),(10005,'自动控制原理','机械学院'),(10006,'大学英语1','外国语学院'),(10007,'运筹学','经济管理学院'),(10008,'运筹学','经济管理学院'),(10009,'大学物理','基础课程'),(10010,'高等数学','基础课程');
/!40000 ALTER TABLE dy_topic_group ENABLE KEYS */;
UNLOCK TABLES;

-- Table structure for table dy_tu

DROP TABLE IF EXISTS dy_tu;
CREATE TABLE dy_tu (
TUID int(11) NOT NULL auto_increment,
UID int(11) default NULL,
TGID int(11) default NULL,
PRIMARY KEY (TUID),
KEY UID (UID),
KEY TGID (TGID),
CONSTRAINT dy_tu_ibfk_1 FOREIGN KEY (UID) REFERENCES dy_user (UID) ON DELETE CASCADE,
CONSTRAINT dy_tu_ibfk_2 FOREIGN KEY (TGID) REFERENCES dy_topic_group (TGID) ON DELETE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

-- Dumping data for table dy_tu

LOCK TABLES dy_tu WRITE;
/*!40000 ALTER TABLE dy_tu DISABLE KEYS /;
INSERT INTO dy_tu VALUES (1,2,10000),(2,2,10001),(3,2,10002),(4,1,10001),(6,1,10005),(10,3,10002),(12,1,10000),(13,1,10002),(14,3,10001),(15,4,10001),(17,7,10001);
/!40000 ALTER TABLE dy_tu ENABLE KEYS */;
UNLOCK TABLES;

-- Table structure for table dy_user

DROP TABLE IF EXISTS dy_user;
CREATE TABLE dy_user (
UID int(11) NOT NULL auto_increment,
UName varchar(20) NOT NULL,
UPwd varchar(20) NOT NULL,
UGender char(2) default '男',
UEmail varchar(40) default NULL,
URole int(11) default '0',
UHead varchar(50) default 'UserHead/no_head.jpg',
URegDate date default NULL,
ULastLogin datetime default NULL,
ULastEmit datetime default NULL,
UPermit int(11) default '1',
PRIMARY KEY (UID),
UNIQUE KEY UName (UName)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

-- Dumping data for table dy_user

LOCK TABLES dy_user WRITE;
/*!40000 ALTER TABLE dy_user DISABLE KEYS /;
INSERT INTO dy_user VALUES (1,'xyz','123456','男','[e-mail]',0,'UserHead/1.jpg','2008-12-08','2009-03-16 22:16:20','2009-03-16 21:00:10',1),(2,'zrk','123456','男','[e-mail]',1,'UserHead/2.JPG','2008-12-08','2009-03-16 23:12:04','2008-12-12 13:27:24',1),(3,'胡再芬','123456','女','[e-mail]',0,'UserHead/3.jpg','2008-12-08','2008-12-12 09:26:47',NULL,1),(4,'wyf','123456','男','[e-mail]',3,'UserHead/1.jpg','2008-12-08','2009-03-17 15:11:32','2008-12-12 14:01:29',1),(5,'fdsa','123123','男','[e-mail]',0,'UserHead/no_head.jpg','2009-03-16','2009-03-16 17:41:24','2009-03-16 17:41:24',1),(7,'wfa','123123','男','[e-mail]',0,'UserHead/no_head.jpg','2009-03-16','2009-03-16 17:44:32','2009-03-16 17:44:32',1),(8,'few','123123','男','[e-mail]',0,'UserHead/no_head.jpg','2009-03-16','2009-03-16 17:45:11','2009-03-16 17:45:11',1);
/!40000 ALTER TABLE dy_user ENABLE KEYS /;
UNLOCK TABLES;
/!40103 SET TIME_ZONE=@OLD_TIME_ZONE */;

/*!40101 SET SQL_MODE=@OLD_SQL_MODE /;
/!40014 SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS /;
/!40014 SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS /;
/!40101 SET CHARACTER_SET_CLIENT=@OLD_CHARACTER_SET_CLIENT /;
/!40101 SET CHARACTER_SET_RESULTS=@OLD_CHARACTER_SET_RESULTS /;
/!40101 SET COLLATION_CONNECTION=@OLD_COLLATION_CONNECTION /;
/!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;

-- Dump completed on 2009-03-17 7:23:17

红色部分不知道什么意思，如果能解释下这几个表的关系，就更好了

Answer 1

[quote]CONSTRAINT dy_apply_ibfk_1 FOREIGN KEY (UID) REFERENCES `dy_use[/quote]
这个是定义外健

[quote]LOCK TABLES dy_revert WRITE[/quote]
这个是锁表,他在插入前都锁了下,插完解锁[quote]UNLOCK TABLES; [/quote]