C. Connect to MySQL

Apt-Get install libmysqlclient-Dev

MySQL uses XAMPP and needs to specify sock

Source code: Main. c

 # If Defined (_ Win32) | defined (_ win64) //  To support Compilation on Windows  # Include <Windows. h> # Endif  # Include <Stdio. h> # Include <Stdlib. h> # Include <MySQL/MySQL. h> //  On my machine, the file is in/usr/local/include/MySQL.  // Define the macros for database operations, or write them directly after they are not definedCode  # Define Select_query "select username from test where userid = % d" Int Main ( Int Argc, Char ** Argv) //  Char ** argv is equivalent to char * argv []  {MySQL, * Sock; //  Defines the database connection handle, which is used by almost all MySQL functions. Mysql_res * res; //  Query Result set, structure type Mysql_field * FD; //  Structure Containing Field Information Mysql_row row; //  String Array that stores the query results of a row      Char Qbuf [ 160 ]; //  Stores query SQL statement strings          If (Argc! = 2 ){ //  Check input parameters Fprintf (stderr, " Usage: mysql_select <userid> \ n  "  ); Exit (  1  );} Mysql_init ( & MySQL );  If (! (Sock = mysql_real_connect (& MySQL, "  Localhost  " , "  Root  " , "" ,"  Test  " , 3306 , "  /Opt/lampp/var/MySQL. Sock  " , 0  ) {Fprintf (stderr,  "  Couldn't connect to engine! \ N % s \ n  " , Mysql_error (& MySQL); perror (  ""  ); Exit ( 1  );} Sprintf (qbuf, select_query, atoi (argv [  1  ]);  If  (Mysql_query (sock, qbuf) {fprintf (stderr,  "  Query failed (% s) \ n  "  , Mysql_error (sock); exit (  1  );}  If (! (RES = Mysql_store_result (sock) {fprintf (stderr, "  Couldn't get result from % s \ n  "  , Mysql_error (sock); exit (  1  );} Printf (  "  Number of fields returned: % d \ n  "  , Mysql_num_fields (RES ));  While (ROW = Mysql_fetch_row (RES) {printf (  "  Ther userid # % d's username is: % s \ n " , Atoi (argv [ 1 ]), (Row [ 0 ] = NULL )&&(! Strlen (row [ 0 ])? "  Null  " : Row [ 0  ]); Puts (  "  Query OK! \ N  "  );} Mysql_free_result (RES); mysql_close (sock); exit (  0 );  Return   0 ; //  . To be compatible with most compilers, add this line }

Compile:

 
 Gcc-O mysql_select./Main. C-lmysqlclient
 

 

 

Simple class Encapsulation

Test. SQL

Mysql> use test;

Mysql> source ~ /Test. SQL;

 Drop   Table   If   Exists  'Test '; /*  ! 40101 set @ saved_cs_client = @ character_set_client  */  ;  /*  ! 40101 set character_set_client = utf8  */  ;  Create   Table  'Test' ('id'  Int ( 11 ) Not   Null Auto_increment, 'value'  Text  ,  Primary   Key  ('Id') Engine  = InnoDB auto_increment =  6   Default Charset =  Latin1;  /*  ! 40101 set character_set_client = @ saved_cs_client  */ ;  ----  Dumping data for table 'test'  --  Lock tables 'test' write;  /*  ! 40000 alter table 'test' disable keys  */  ;  Insert   Into 'Test' Values ( 1 , '  Hxl ' ),( 2 , '  SQLite  ' ),( 3 , '  Test  ' ),( 4 , '  For  ' ),( 5 ,'  Linux  '  );  /*  ! 40000 alter table 'test' 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 23:52:14 

 

Main. CC

# Include <cstdlib> # Include <Fstream> # Include <Iomanip># Include <Iostream> Extern   "  C  "  {# Include <MySQL/MySQL. h> # Include < String . H> }  Using   Namespace  STD;  Class  Mydb {  Private : MySQL, * Sock; //  Defines the database connection handle, which is used by almost all MySQL functions. Mysql_res * res; //  Query Result set, structure type Mysql_field * FD; //  Structure Containing Field Information Mysql_row row; //  String Array that stores the query results of a row      Public  : Mydb () {cout < "  Nothing " < Endl;} mydb (  Char * IP, Char * User, Char * Passwd, Char * Db_name, Int Port, Char * Socket) {mysql_init ( & MySQL );  If (! (Sock = mysql_real_connect (& MySQL, IP, user, passwd, db_name, port, socket, 0 ) {Fprintf (stderr,  "  Couldn't connect to engine! \ N % s \ n  " , Mysql_error (& MySQL); perror (  ""  ); Exit (  1  );}} ~ Mydb () {mysql_free_result (RES); mysql_close (sock); cout < "  Connect destoryed " < Endl ;}  Void    Get ( Char * Str ){  If  (Mysql_query (sock, STR) {fprintf (stderr,  "  Query failed (% s) \ n  "  , Mysql_error (sock); exit (  1  );} If (! (RES = Mysql_store_result (sock) {fprintf (stderr,  "  Couldn't get result from % s \ n  "  , Mysql_error (sock); exit (  1  );} Printf (  "  Number of fields returned: % d \ n  "  , Mysql_num_fields (RES ));  While (ROW =Mysql_fetch_row (RES) {printf (  "  Ther username is: % s \ n  " , (Row [ 0 ] = NULL )&&(! Strlen (row [ 0 ])? "  Null  " : Row [ 0  ]); Puts (  "  Query OK!  " );}}};  Int  Main (  Int Argc, Char * Argv []) {mydb test (  "  Localhost  " , "  Root  " , "" , "  Test " , 3306 , "  /Opt/lampp/var/MySQL. Sock  "  ); Test.  Get ( "  Select value from test where id = 1  "  );  Return  Exit_success ;}  //  ---------- End of function main ---------- 

 

 

Compile:

G ++-g-o mysql_select./MySQL. CC-lmysqlclient

 

End