C/C++连接MySQL数据库执行查询（以employees数据库为对象进行查询）
1 /*
2 C/C++连接MySQL数据库时，需要包含一个*.h的mysql头文件和一个mysql的lib文件
3 1、初始化；
4 2、连接数据库；
5 3、执行sql查询语句；
6 4、获取查询值；
7 5、关闭
8 */
9 #include <stdio.h>
10 #include <WinSock.h>
11 #include <mysql.h>
12 #include <Windows.h>
13 #pragma comment(lib,"wsock32.lib")
14 #pragma comment(lib,"libmysql.lib")
15
16 MYSQL mysql;
17 MYSQL_FIELD *fd; //字段列数组
18 char field[32][32]; //存字段名二维数组
19 MYSQL_RES *res; //行的一个查询结果集
20 MYSQL_ROW column; //数据行的列
21 char query[150]; //查询语句
22
23 //函数声明
24 bool ConnectDatabase();
25 void FreeConnect();
26 bool QueryDatabase();
27 bool InsertData();
28 bool ModifyData();
29 bool DeleteData();
30
31 int main(int argc, char **argv){
32 ConnectDatabase();
33 QueryDatabase();
34 InsertData();
35 QueryDatabase();
36 ModifyData();
37 QueryDatabase();
38 //DeleteData();
39 //QueryDatabase();
40 FreeConnect();
41 system("pause");
42 return 0;
43 }
44
45 //连接数据库
46 bool ConnectDatabase(){
47 //Gets or initializes a MYSQL structure
48 mysql_init(&mysql);
49
50 // Connects to a MySQL server
51 const char host[] = "localhost";
52 const char user[] = "root";
53 const char passwd[] = "root";
54 const char db[] = "employees";
55 unsigned int port = 3306;
56 const char *unix_socket = NULL;
57 unsigned long client_flag = 0;
58
59 //A MYSQL* connection handler if the connection was successful,
60 //NULL if the connection was unsuccessful. For a successful connection,
61 //the return value is the same as the value of the first parameter.
62 if (mysql_real_connect(&mysql, host, user, passwd, db, port, unix_socket, client_flag)){
63 printf("The connection was successful.\n");
64 return true;
65 }
66 else{
67 //const char *mysql_error(MYSQL *mysql)
68 //Returns the error message for the most recently invoked MySQL function
69 //A null-terminated character string that describes the error.
70 //An empty string if no error occurred.
71 printf("Error connecting to database:%s\n", mysql_error(&mysql));
72 return false;
73 }
74 }
75
76 //释放资源
77 //void mysql_free_result(MYSQL_RES *result)
78 //Frees the memory allocated for a result set by mysql_store_result(),
79 //mysql_use_result(), mysql_list_dbs(), and so forth.
80 //When you are done with a result set, you must free the memory it
81 //uses by calling mysql_free_result().
82 //Do not attempt to access a result set after freeing it.
83
84 //void mysql_close(MYSQL *mysql)
85 //Closes a previously opened connection.mysql_close() also deallocates
86 //the connection handler pointed to by mysql if the handler was allocated automatically
87 //by mysql_init() or mysql_connect().
88 void FreeConnect(){
89 mysql_free_result(res);
90 mysql_close(&mysql);
91 }
92
93 //查询数据
94 bool QueryDatabase(){
95 //将数据格式化输出到字符串
96 sprintf_s(query, "select * from departments");
97 //设置编码格式
98 mysql_query(&mysql, "set names gbk");
99
100 //int mysql_query(MYSQL *mysql, const char *stmt_str)
101 //Executes an SQL query specified as a null-terminated string
102 //Executes the SQL statement pointed to by the null-terminated string stmt_str.
103 //Normally, the string must consist of a single SQL statement without a terminating semicolon (;) or \g.
104 //If multiple-statement execution has been enabled, the string can contain several statements separated by semicolons.
105 //Return Values:Zero for success.Nonzero if an error occurred.
106 if (mysql_query(&mysql, query)){
107 printf("Query failed (%s)\n", mysql_error(&mysql));
108 return false;
109 }
110 else{
111 printf("query success\n");
112 }
113
114 //MYSQL_RES *mysql_store_result(MYSQL *mysql)
115 //Retrieves a complete result set to the client
116 //mysql_store_result() reads the entire result of a query to the client, allocates a MYSQL_RES structure, and places the result into this structure.
117 //mysql_store_result() returns a null pointer if the statement did not return a result set(for example, if it was an INSERT statement).
118 //mysql_store_result() also returns a null pointer if reading of the result set failed.
119 //You can check whether an error occurred by checking whether mysql_error() returns a nonempty string.
120 //Return Values: A MYSQL_RES result structure with the results.NULL(0) if an error occurred.
121 res = mysql_store_result(&mysql);
122 if (!res){
123 printf("Couldn‘t get result from %s\n", mysql_error(&mysql));
124 return false;
125 }
126
127 //my_ulonglong mysql_affected_rows(MYSQL *mysql)
128 //It returns the number of rows changed, deleted,
129 //or inserted by the last statement if it was an UPDATE, DELETE, or INSERT.
130 //For SELECT statements, returns the number of rows in the result set.
131 printf("number of dataline returned: %d\n", mysql_affected_rows(&mysql));
132
133 //获取字段的信息
134 //MYSQL_FIELD *mysql_fetch_field(MYSQL_RES *result)
135 //Returns the definition of one column of a result set as a MYSQL_FIELD structure.
136 //Call this function repeatedly to retrieve information about all columns in the result set.
137
138 // 获取列数
139 int j = mysql_num_fields(res);
140
141 char *str_field[32]; //存储字段信息
142
143 //获取字段名
144 for (int i = 0; i < j; i++){
145 str_field[i] = mysql_fetch_field(res)->name;
146 }
147
148 //打印字段
149 for (int i = 0; i < j; i++)
150 printf("%10s\t", str_field[i]);
151 printf("\n");
152
153 //打印查询结果
154 //MYSQL_ROW mysql_fetch_row(MYSQL_RES *result)
155 //Fetches the next row from the result set
156 while (column = mysql_fetch_row(res)){
157 printf("%10s\t%10s\n", column[0], column[1]);
158 }
159 return true;
160 }
161
162 //插入数据
163 bool InsertData()
164 {
165 sprintf_s(query, "insert into departments values (‘dddd‘, ‘xxxxx‘);");
166 if (mysql_query(&mysql, query)) {
167 printf("Query failed (%s)\n", mysql_error(&mysql));
168 return false;
169 }
170 else{
171 printf("Insert success\n");
172 return true;
173 }
174 }
175
176 //修改数据
177 bool ModifyData(){
178 sprintf_s(query, "update departments set dept_name=‘yyyyy‘ where dept_no=‘dddd‘");
179 if (mysql_query(&mysql, query)) {
180 printf("Query failed (%s)\n", mysql_error(&mysql));
181 return false;
182 }
183 else{
184 printf("Insert success\n");
185 return true;
186 }
187 }
188
189 //删除数据
190 bool DeleteData()
191 {
192 sprintf_s(query, "delete from departments where dept_no=‘dddd‘;");
193 //char query[100];
194 //printf("please input the sql:\n");
195 //gets_s(query); //手动输入sql语句
196 if (mysql_query(&mysql, query)) {
197 printf("Query failed (%s)\n", mysql_error(&mysql));
198 return false;
199 }
200 else{
201 printf("Insert success\n");
202 return true;
203 }
204 }
原文地址：https://www.cnblogs.com/iwangzhengchao/p/10056075.html
时间： 2024-10-08 13:05:29