使用C语言访问MySQL数据库
MySQL数据库（管理CD盘）
一、数据库设计
1、数据库E/R图（实体-关系图）应该是多对多，为了简化，一对多（把artist的key——Artist_ID放到CD中作为外键）
2、关系模式（Relation Schema）
Artist(artist_ID, names) 简称为D1表
CD(CD_ID, Title, cataloge, Notes, artist_id（外键）,track_id（磁道）, song_name)
其中：非主属性track_id, song_name,不能完全函数依赖于键CD_ID, 不符合第二范式，将其投影分解为：
CD(CD_ID,Title, cataloge, Notes, artist_id) 简称为D2表
Track(CD_ID,track_id, song_name) 简称为D3表
//甲骨文数据库可以分属性为多个属性，可以直接存图片或者MP3
二、创建数据库
1、进入MySQL数据库
%mysql –u root –p
Password:
2、生成数据库
mysql> create database ex1;
Query OK, 1 row affected (0.01 sec)
2、授权：
用户的授权信息保存于mysql数据库中的user表中
例：mysql>use mysql;
mysql>select user, host, passwordfrom user;
授权语法：
grant all on 数据库名.表名 to ‘用户名’@’客户登录计算机名（地址）’ identified by ‘密码’;
或
grant allprivileges on数据库名.表名 to 用户名@客户登录计算机名（地址） identified by ‘密码’;
或
grant allon 数据库名.表名 to 用户名@客户登录计算机名（地址） identified by ‘密码’;
例：mysql>grant all on *.* to test@localhost identified by ‘password’;
mysql>use mysql; 打开MySQL数据库
mysql>update user 更新user表
>set password=OLD_PASSWORD('password')
>where user='test';
mysql>flush privileges;
或
mysql>grant all on ex110301.* tow12@localhost identified by ‘password’;
mysql>use mysql; 打开MySQL数据库
mysql>flush privileges;
或
mysql>grant all on ex110301.* tow12@'%' identified by 'password';
mysql>use mysql; 打开MySQL数据库
mysql>flush privileges;
mysql>exit
表示用户w12对cd110301具有所有权限，可从任何计算（‘%’）上连接该数据库
说明：远程连接需要使用TCP端口：3306
3、改用你授权的用户名/密码登录
%mysql –u 授权的用户名 -p
Password:输入授权密码
4、创建表
4.1 生成表cd
create table cd (
id INTEGER AUTO_INCREMENT NOT NULLPRIMARY KEY,
title VARCHAR(70) NOT NULL,
artist_id INTEGER NOT NULL,
catalogue VARCHAR(30) NOT NULL
);
4.2 生成表artist
create tableartist (
id INTEGER AUTO_INCREMENT NOT NULLPRIMARY KEY,
name VARCHAR(100) NOT NULL
);
4.3 生成表track
create table track(
cd_id INTEGER NOT NULL,
track_id INTEGER NOT NULL,
title VARCHAR(70),
PRIMARY KEY(cd_id, track_id)
);
三、插入数据
3.1 向表artist中插入数据
insert intoartist(id, name) values(1, 'Pink Floyd');
insert intoartist(id, name) values(2, 'Genesis');
insert intoartist(id, name) values(3, 'Einaudi');
insert intoartist(id, name) values(4, 'Melanie C');
3.2 向表cd中插入数据
insert into cd(id,title, artist_id, catalogue) values(1, 'Dark Side of the Moon', 1, 'B000024D4P');
insert into cd(id,title, artist_id, catalogue) values(2, 'Wish You Were Here', 1, 'B000024D4S');
insert into cd(id,title, artist_id, catalogue) values(3, 'A Trick of the Tail', 2, 'B000024EXM');
insert into cd(id,title, artist_id, catalogue) values(4, 'Selling England By the Pound', 2,'B000024E9M');
insert into cd(id,title, artist_id, catalogue) values(5, 'I Giorni', 3, 'B000071WEV');
insert into cd(id,title, artist_id, catalogue) values(6, 'Northern Star', 4, 'B00004YMST');
3.3 向表track中插入数据
insert intotrack(cd_id, track_id, title) values(1, 1, 'Speak to me');
insert intotrack(cd_id, track_id, title) values(1, 2, 'Breathe');
insert intotrack(cd_id, track_id, title) values(1, 3, 'On the run');
insert intotrack(cd_id, track_id, title) values(1, 4, 'Time');
insert intotrack(cd_id, track_id, title) values(1, 5, 'Great gig in the sky');
insert intotrack(cd_id, track_id, title) values(1, 6, 'Money');
insert intotrack(cd_id, track_id, title) values(1, 7, 'Us and them');
insert intotrack(cd_id, track_id, title) values(1, 8, 'Any colour you like');
insert intotrack(cd_id, track_id, title) values(1, 9, 'Brain damage');
insert intotrack(cd_id, track_id, title) values(1, 10, 'Eclipse');
insert intotrack(cd_id, track_id, title) values(2, 1, 'Shine on you crazy diamond');
insert intotrack(cd_id, track_id, title) values(2, 2, 'Welcome to the machine');
insert intotrack(cd_id, track_id, title) values(2, 3, 'Have a cigar');
insert intotrack(cd_id, track_id, title) values(2, 4, 'Wish you were here');
insert intotrack(cd_id, track_id, title) values(2, 5, 'Shine on you crazy diamond pt.2');
insert intotrack(cd_id, track_id, title) values(3, 1, 'Dance on a volcano');
insert intotrack(cd_id, track_id, title) values(3, 2, 'Entangled');
insert intotrack(cd_id, track_id, title) values(3, 3, 'Squonk');
insert intotrack(cd_id, track_id, title) values(3, 4, 'Madman moon');
insert intotrack(cd_id, track_id, title) values(3, 5, 'Robbery assault and battery');
insert intotrack(cd_id, track_id, title) values(3, 6, 'Ripples');
insert intotrack(cd_id, track_id, title) values(3, 7, 'Trick of the tail');
insert intotrack(cd_id, track_id, title) values(3, 8, 'Los Endos');
四、查询
4.1 获取cd表的最后一个记录号（取出游标）
Select LAST_INSERT_ID();
结果： +---------------------------+
| LAST_INSERT_ID() |
+---------------------------+
| 0 |
+---------------------------+
因为自己定义的id所以没有自增，所以为0，若第一个属性变为null，再插入，则会变为7，即cd表中的最后一个id。
4.2 列出track表中第3张cd光盘中的所有曲目
Select track_id, title from track wheretrack.cd_id=3;
结果： +-------------+-------------------------------------------+
| track_id | title |
+------------+--------------------------------------------+
| 1 | Dance on a volcano |
| 2 |Entangled |
| 3 | Squonk |
| 4 | Madman moon |
| 5 | Robbery assault and battery |
| 6 | Ripples |
| 7 | Trick of the tail |
| 8 | Los Endos |
+-------------+-------------------------------------------+
4.3 多表查询
列出第二张cd中，艺术家的名字存放在artist表中的艺术家名、编号、cd名称及分类号
Selectartist.name, artist.id, cd.id, cd.title, cd.catalogue from artist, cd where artist.id=cd.artist_id andcd.id=2;
结果： +--------------+----+----+--------------------------+-------------------+
| name | id | id | title |catalogue |
+--------------+----+----+--------------------------+-------------------+
| Pink Floyd | 1 | 2 | Wish You Were Here | B000024D4S|
+--------------+----+----+--------------------------+-------------------+
4.4 模糊查询
查询艺术家名字带有gene???，或cd光盘的光盘名中带有Trick的艺术家编号和cd编号
Selectdistinct artist.id, cd.id from artist, cd where artist.name LIKE '%%gene%%' orcd.title LIKE '%%Trick%%';
其中：distinct 为消除冗余记录，数据库术语为投影
结果+----+------+
| id | id |
+----+------+
| 2 | 1|
| 2 | 2|
| 1 | 3|
| 2 | 3|
| 3 | 3|
| 4 | 3|
| 2 | 4|
| 2 | 5|
| 2 | 6|
+-----+------+
4.5 子查询
列出与第二张光盘对应的艺术家id(artist_id)
Selectartist_id from cd where artist_id=(select artist_id from cd where id=2);
结果：+-----------+
| artist_id |
+-----------+
| 1 |
| 1 |
+-----------+
使用C语言访问创建的数据库
1. 头文件---app_mysql.h
定义数据结构体和函数原型
1.1 表示当前CD的数据结构（不考虑track曲目信息）
structcurrent_cd_st {
int artist_id;
int cd_id;
char artist_name[100];
char title[100];
char catalogue[100];
};
1.2 一张CD盘中的曲目数据结构
structcurrent_tracks_st {
int cd_id;
char track[20][100];
};
#defineMAX_CD_RESULT 10
structcd_search_st {
int cd_id[MAX_CD_RESULT];
};
1.3 数据库操作函数原型
1.3.1 打开/关闭数据库函数原型
int database_start(char *name, char *password);
voiddatabase_end();
1.4 增加CD和曲目的函数原型
int add_cd(char*artist, char *title, char *catalogue, int *cd_id);
intadd_tracks(struct current_tracks_st *tracks);
1.5 查询和返回CD盘信息的函数原型
int find_cds(char*search_str, struct cd_search_st *results);
int get_cd(intcd_id, struct current_cd_st *dest);
intget_cd_tracks(int cd_id, struct current_tracks_st *dest);
1.6 从数据库中删除CD的函数原型
int delete_cd(intcd_id);
2、主程序---app_test.c
用于测试函数实现的是否正确的函数原型
#include
#include
#include
#include"app_mysql.h"
int main() {
struct current_cd_st cd;
struct cd_search_st cd_res;
struct current_tracks_st ct; //曲目的数据结构
int cd_id;
int res, i;
database_start("n1417", "密码");
res = add_cd("Mahler","Symphony No 1", "4596102", &cd_id);
printf("Result of adding a cd was %d,cd_id is %d\n", res, cd_id);
memset(&ct, 0, sizeof(ct));
ct.cd_id = cd_id;
strcpy(ct.track[0], "LansamSchleppend");
strcpy(ct.track[1], "Kraftigbewegt");
strcpy(ct.track[2], "Feierlich undgemesen");
strcpy(ct.track[3], "Sturmischbewegt");
add_tracks(&ct);
res =find_cds("Symphony", &cd_res);
//以symphony为关键字查找相关的CD，找到的结果给cd_res
printf("Found %d cds, first has ID%d\n", res, cd_res.cd_id[0]);
res = get_cd(cd_res.cd_id[0], &cd);
//找到的CD中第一张CD的相关信息
printf("get_cd returned %d\n",res);
memset(&ct, 0, sizeof(ct)); //置0
res = get_cd_tracks(cd_res.cd_id[0],&ct); //列出这张CD中的曲目
printf("get_cd_tracks returned%d\n", res);
printf("Title: %s\n", cd.title);
i = 0;
while (i < res) {
printf("\ttrack %d is %s\n", i, ct.track[i]); //输出曲目名
i++;
}
res = delete_cd(cd_res.cd_id[0]); //删除CD表上这张CD并删除track表中这张CD上的所有曲目
printf("Delete_cd returned %d\n",res);
database_end();
return EXIT_SUCCESS;
}
3、函数实现---app_mysql.c
用于实现app_mysql.h头文件中定义的函数原型
#include
#include
#include
#include"mysql.h"
#include"app_mysql.h"
static MYSQLmy_connection;
static intdbconnected = 0; 用于判断是否已经建立连接的变量 0未建立，其它：建立
static intget_artist_id(char *artist);
3.1 建立数据库连接的函数实现
intdatabase_start(char *name, char *pwd) {
if (dbconnected) return 1;
____ mysql_init(&my_connection);
if(!mysql_real_connect(&my_connection, "localhost","root",NULL,"labn1417", 0, NULL, 0)) {
fprintf(stderr,"Database connection failure: %d, %s\n",mysql_errno(&my_connection), mysql_error(&my_connection));
return 0;
}___________________________________________________
dbconnected = 1;
return 1;
} /* databasestart */
3.2 关闭数据库连接的函数实现
voiddatabase_end() {
if (dbconnected)mysql_close(&my_connection);
dbconnected = 0;
} /* database_end*/
3.3 向数据库中添加记录的函数实现
int add_cd(char*artist, char *title, char *catalogue, int *cd_id) {
MYSQL_RES *res_ptr;
MYSQL_ROW mysqlrow;
int res;
char is[250];
char es[250];
int artist_id = -1;
int new_cd_id = -1;
if (!dbconnected) return 0;
artist_id = get_artist_id(artist);
mysql_escape_string(es, title,strlen(title));
sprintf(is, "INSERT INTO cd(title,artist_id, catalogue) VALUES('%s', %d, '%s')", es, artist_id, catalogue);
res = mysql_query(&my_connection, is);
if (res) {
fprintf(stderr, "Insert error %d:%s\n", mysql_errno(&my_connection), mysql_error(&my_connection));
return 0;
}
res = mysql_query(&my_connection,"SELECT LAST_INSERT_ID()");
if (res) {
printf("SELECT error: %s\n",mysql_error(&my_connection));
return 0;
} else {
res_ptr =mysql_use_result(&my_connection);
if (res_ptr) {
if ((mysqlrow =mysql_fetch_row(res_ptr))) {
sscanf(mysqlrow[0], "%d",&new_cd_id);
}
mysql_free_result(res_ptr);
}
*cd_id = new_cd_id;
if (new_cd_id != -1) return 1;
return 0;
}
} /* add_cd */
3.4 向数据库中添加artist的函数实现
/* Find or createan artist_id for the given string */
static intget_artist_id(char *artist) {
MYSQL_RES *res_ptr;
MYSQL_ROW mysqlrow;
int res;
char qs[250];
char is[250];
char es[250];
int artist_id = -1;
/* Does it already exist? */
mysql_escape_string(es, artist,strlen(artist));
sprintf(qs, "SELECT id FROM artist WHEREname = '%s'", es);
res = mysql_query(&my_connection, qs);
if (res) {
fprintf(stderr, "SELECT error:%s\n", mysql_error(&my_connection));
} else {
res_ptr =mysql_store_result(&my_connection);
if (res_ptr) {
if (mysql_num_rows(res_ptr) > 0) {
if (mysqlrow = mysql_fetch_row(res_ptr)){
sscanf(mysqlrow[0], "%d", &artist_id);
}
}
mysql_free_result(res_ptr);
}
}
if (artist_id != -1) return artist_id;
sprintf(is, "INSERT INTO artist(name)VALUES('%s')", es);
res = mysql_query(&my_connection, is);
if (res) {
fprintf(stderr, "Insert error %d:%s\n", mysql_errno(&my_connection), mysql_error(&my_connection));
return 0;
}
res = mysql_query(&my_connection,"SELECT LAST_INSERT_ID()");
if (res) {
printf("SELECT error: %s\n",mysql_error(&my_connection));
return 0;
} else {
res_ptr =mysql_use_result(&my_connection);
if (res_ptr) {
if ((mysqlrow =mysql_fetch_row(res_ptr))) {
sscanf(mysqlrow[0], "%d",&artist_id);
}
mysql_free_result(res_ptr);
}
}
return artist_id;
} /* get_artist_id*/
3.5 向数据库中添加曲目的函数实现
intadd_tracks(struct current_tracks_st *tracks) {
int res;
char is[250]; CD盘名称
char es[250]; 一张CD盘上的曲目
int i;
if (!dbconnected) return 0;
i = 0;
while (tracks->track[i][0]) {
______ mysql_escape_string(es,tracks->track[i], strlen(tracks->track[i])); //用于对特殊字符进行转义处理
sprintf(is,"INSERT INTO track(cd_id, track_id, title) VALUES(%d, %d, '%s')",tracks->cd_id, i + 1, es); //向track表插入cd_id为cd_id、track_id为i+1, title为es的曲目
res= mysql_query(&my_connection, is);
if (res) {
fprintf(stderr,"Insert error %d: %s\n", mysql_errno(&my_connection),mysql_error(&my_connection));
return 0;
}
i++;
}
return 1;
} /* add_tracks */
3.6 查询CD盘信息的函数实现
int get_cd(intcd_id, struct current_cd_st *dest) {
MYSQL_RES *res_ptr;
MYSQL_ROW mysqlrow;
int res;
char qs[250];
if (!dbconnected) return 0;
memset(dest, 0, sizeof(*dest));
dest->artist_id = -1;
sprintf(qs, "SELECT artist.id, cd.id,artist.name, cd.title, cd.catalogue FROM artist, cd WHERE artist.id =cd.artist_id and cd.id = %d", cd_id);
res = mysql_query(&my_connection, qs);
if (res) {
fprintf(stderr, "SELECT error:%s\n", mysql_error(&my_connection));
} else {
res_ptr =mysql_store_result(&my_connection);
if (res_ptr) {
if (mysql_num_rows(res_ptr) > 0) {
if (mysqlrow = mysql_fetch_row(res_ptr)){
sscanf(mysqlrow[0], "%d", &dest->artist_id);
sscanf(mysqlrow[1], "%d", &dest->cd_id);
strcpy(dest->artist_name, mysqlrow[2]);
strcpy(dest->title, mysqlrow[3]);
strcpy(dest->catalogue, mysqlrow[4]);
}
}
mysql_free_result(res_ptr);
}
}
if (dest->artist_id != -1) return 1;
return 0;
} /* get_cd */
3.7 查询一张盘中曲目信息的函数实现
int get_cd_tracks(intcd_id, struct current_tracks_st *dest) {
MYSQL_RES *res_ptr;
MYSQL_ROW mysqlrow;
int res;
char qs[250];
int i = 0, num_tracks = 0;
if (!dbconnected) return 0;
memset(dest, 0, sizeof(*dest));
dest->cd_id = -1;
sprintf(qs, "SELECT track_id, title FROMtrack WHERE track.cd_id = %d ORDER BY track_id", cd_id);
res = mysql_query(&my_connection, qs);
if (res) {
fprintf(stderr, "SELECT error:%s\n", mysql_error(&my_connection));
} else {
res_ptr = mysql_store_result(&my_connection);
if (res_ptr) {
if ((num_tracks = mysql_num_rows(res_ptr))> 0) {//个数不为空
while(mysqlrow = mysql_fetch_row(res_ptr)) {//循环获得结果的每一行
strcpy(dest->track[i], mysqlrow[1]);
//取出一个记录的第二属性值 ，并将其赋值给dest。
i++;
}
dest->cd_id= cd_id;
}
mysql_free_result(res_ptr);
}
}
return num_tracks;
} /* get_cd_tracks*/
3.8 模糊查找CD盘
int find_cds(char*search_str, struct cd_search_st *dest) {
MYSQL_RES *res_ptr;
MYSQL_ROW mysqlrow;
int res;
char qs[500];
int i = 0;
char ss[250];
int num_rows = 0;
if (!dbconnected) return 0;
memset(dest, -1, sizeof(*dest));
mysql_escape_string(ss, search_str,strlen(search_str));
sprintf(qs, "SELECT DISTINCT artist.id,cd.id FROM artist, cd WHERE artist.id = cd.artist_id and (artist.name LIKE'%%%s%%' OR cd.title LIKE '%%%s%%' OR cd.catalogue LIKE '%%%s%%')", ss,ss, ss);
res = mysql_query(&my_connection, qs);
if (res) {
fprintf(stderr, "SELECT error:%s\n", mysql_error(&my_connection));
} else {
res_ptr =mysql_store_result(&my_connection);
if (res_ptr) {
num_rows = mysql_num_rows(res_ptr);
if ( num_rows > 0) {
while ((mysqlrow =mysql_fetch_row(res_ptr)) && i < MAX_CD_RESULT) {
sscanf(mysqlrow[1], "%d", &dest->cd_id[i]);
i++;
}
}
mysql_free_result(res_ptr);
}
}
return num_rows;
} /* find_cds */
3.9 删除一张CD盘中的相关信息
int delete_cd(intcd_id) {
int res;
char qs[250];
int artist_id, num_rows;
MYSQL_RES *res_ptr;
MYSQL_ROW mysqlrow;
if (!dbconnected) return 0;
artist_id = -1;
sprintf(qs, "SELECT artist_id FROM cdWHERE artist_id = (SELECT artist_id FROM cd WHERE id = '%d')", cd_id);
res = mysql_query(&my_connection, qs);
if (res) {
fprintf(stderr, "SELECT error:%s\n", mysql_error(&my_connection));
} else {
res_ptr =mysql_store_result(&my_connection);
if (res_ptr) {
num_rows = mysql_num_rows(res_ptr);
if (num_rows == 1) {
/* Artist not used by any other CDs */
mysqlrow = mysql_fetch_row(res_ptr);
sscanf(mysqlrow[0], "%d",&artist_id);
}
mysql_free_result(res_ptr);
}
}
sprintf(qs, "DELETE FROM track WHEREcd_id = '%d'", cd_id);
res = mysql_query(&my_connection, qs);
if (res) {
fprintf(stderr, "Delete error (track)%d: %s\n", mysql_errno(&my_connection),mysql_error(&my_connection));
return 0;
}
sprintf(qs, "DELETE FROM cd WHERE id ='%d'", cd_id);
res = mysql_query(&my_connection, qs);
if (res) {
fprintf(stderr, "Delete error (cd) %d:%s\n", mysql_errno(&my_connection), mysql_error(&my_connection));
return 0;
}
if (artist_id != -1) {
/* artist entry is now unrelated to anyCDs, delete it */
sprintf(qs, "DELETE FROM artist WHEREid = '%d'", artist_id);
res = mysql_query(&my_connection, qs);
if (res) {
fprintf(stderr, "Delete error(artist) %d: %s\n", mysql_errno(&my_connection),mysql_error(&my_connection));
}
}
return 1;
} /* delete_cd */
结果：
Result of adding acd was 1, cd_id is 7
Found 1 cds, firsthas ID 7
get_cd returned 1
get_cd_tracksreturned 4
Title: Symphony No1
track 0 is Lansam Schleppend
track 1 is Kraftig bewegt
track 2 is Feierlich und gemesen
track 3 is Sturmisch bewegt
Delete_cd returned1