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 }