MySQL basics: MySQL and C combined instances

A simple interaction between MySQL and C, using some MySQL C APIs!

Old birds pass by. You can check it out!

/*************************************** * ** This document describes how to use the C interface of MySQL to initialize a database, check whether the database exists. If the database does not exist, create it. Check whether the table exists, if it does not exist, create ************************************* * ***/# include <stdio. h> # include <stdlib. h> # include <string. h> // the header file containing MySQL is required, /usr/include/MySQL //-L/usr/lib/-lmysqlclient-I/usr/include/MySQL option # include <MySQL. h> // basic header file, declaration of some important struct # include <errmsg. h> // store the error message # include <mysql_version.h> // contains the current MySQL version information // All variable, macro definition // # define debug # define server_host "Lo Calhost "// MySQL remote address # define server_user" root "// database login name # define server_pwd" 123 "// database login password # define db_name" tmp_db "// create a database name # define table_name "mytables" // table int check_tbl in the database (MySQL * MySQL, char * Name); int check_db (MySQL * MySQL, char * db_name); int init_db () {int err = 0; MySQL; If (! Mysql_init (& MySQL) {perror ("mysql_init:"); exit (1) ;}if (! Mysql_real_connect (& MySQL, server_host, server_user, server_pwd, null, 0, null, 0) {perror ("mysql_real_connect"); exit (1 );} printf ("connected ..... \ n "); err = check_db (& MySQL, db_name); If (Err! = 0) {printf ("create dB is err! \ N "); mysql_close (& MySQL); exit (1) ;}// select which dB if (mysql_select_db (& MySQL, db_name) // return 0 is success ,! 0 is err {perror ("mysql_select_db:"); mysql_close (& MySQL); exit (1) ;}// chuangjianbiao if (ERR = check_tbl (& MySQL, table_name ))! = 0) {printf ("check_tbl is err! \ N "); mysql_close (& MySQL); exit (1) ;}mysql_close (& MySQL); Return 0 ;}int check_db (MySQL * MySQL, char * db_name) {mysql_row ROW = NULL; mysql_res * res = NULL; Res = mysql_list_dbs (MySQL, null); If (RES) {While (ROW = mysql_fetch_row (RES ))! = NULL) {printf ("DB is % s \ n", row [0]); If (strcmp (row [0], db_name) = 0) {printf ("find dB % s \ n", db_name); break ;}// mysql_list_dbs allocates memory. Use mysql_free_result to release mysql_free_result (RES);} If (! Row) // if this database does not exist, {char Buf [128] = {0} is created; strcpy (BUF, "create database"); strcat (BUF, db_name ); # ifdef debug printf ("% s \ n", Buf); # endif if (mysql_query (MySQL, Buf) {fprintf (stderr, "query failed (% s) \ n ", mysql_error (MySQL); exit (1) ;}} return 0 ;}int check_tbl (MySQL * MySQL, char * Name) {If (name = NULL) return 0; mysql_row ROW = NULL; mysql_res * res = NULL; Res = mysql_list_tables (MySQL, null); If (RES) {whil E (ROW = mysql_fetch_row (RES ))! = NULL) {printf ("tables is % s \ n", row [0]); If (strcmp (row [0], name) = 0) {printf ("find the table! \ N "); break ;}} mysql_free_result (RES);} If (! Row) // create table {char Buf [128] = {0}; char qbuf [128] = {0}; snprintf (BUF, sizeof (BUF ), "% s (name varchar (20), sex char (1), score int (3);", table_name); strcpy (qbuf, "create table "); strcat (qbuf, Buf); // # ifdef debug printf ("% s \ n", qbuf); // # endif if (mysql_query (MySQL, qbuf )) {fprintf (stderr, "query failed (% s) \ n", mysql_error (MySQL); exit (1) ;}} return 0 ;}int main () {int err = 0; err = init_db (); Return 0 ;}

Compilation Method: The last-I must check whether the directory exists. Otherwise, an error is reported.

gcc -o mysql mysql.c -L/usr/lib/ -lmysqlclient -I/usr/include/mysql

Error:

Root @ jack-desktop :~ # Gcc-O MySQL. C-L/usr/lib/-lmysqlclientgcc: mysql. C: no such file or directory root @ jack-desktop :~ # Root @ jack-desktop :~ # Root @ jack-desktop :~ # Cd KYC/root @ jack-desktop: KYC # gcc-O MySQL. c-l/usr/lib/-lmysqlclientmysql. c: 15: 73: Error: MySQL. h: there is no such file or directory MySQL. c: 16: 43: Error: errmsg. h: there is no such file or directory MySQL. c: 17: 63: Error: mysql_version.h: there is no such file or directory MySQL. c: 27: Error: Expected ') 'before' * 'tokenmysql. c: 28: Error: Expected ') 'before' * 'tokenmysql. c: In function 'init _ db': MySQL. c: 34: Error: 'mysql' undeclared (first use in this function) MySQL. c: 34: Error: (each undeclared identifier is reported only oncemysql. c: 34: Error: for each function it appears in .) mySQL. c: 34: Error: Expected '; 'before' MySQL' MySQL. c: 36: Error: 'mysql' undeclared (first use in this function) MySQL. c: at top level: MySQL. c: 73: Error: Expected ') 'before' * 'tokenmysql. c: 109: Error: Expected ') 'before' * 'token