Operate MySQL Databases in C language, and perform operations such as connection, insertion, modification, and deletion.

Many people use MySQL to develop some projects. Sometimes, for the sake of performance, we directly use C language to develop related modules, especially in our web applications, although PHP, JSP, and other scripts provide MySQL interfaces, it is clear that using C language directly has better security and performance, michael used to use this type of interface written in C language in multiple projects developed using PHP before compiling it into php for direct use by php scripts, I will not talk about this topic much. Next I will mainly talk about how to connect to the MySQL database with C language in Linux, read the data returned in it, and compile it at the same time.

Most of the code here is referenced in the MySQL release package. c source file. You can also find the relevant code in it. The following code connects to the 9tmd_bbs_utf8 database on the local MySQL server, obtain the user name from the table tbb_user based on the input userid and print the user name to the terminal.

# If defined (_ WIN32) | defined (_ WIN64) // to support Compilation on windows
# Include <windows. h>
# Endif
# Include <stdio. h>
# Include <stdlib. h>
# Include "mysql. h" // on my machine, the file is in/usr/local/include/mysql.
 
// Define the macros for database operations, or write them directly into the code without defining them.
# Define SELECT_QUERY "select username from tbb_user where userid = % d"
 
Int main (int argc, char ** argv) // char ** argv is equivalent to char * argv []
{
MYSQL 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 the query SQL statement string

If (argc! = 2) {// check the input parameters
Fprintf (stderr, "usage: mysql_select <userid> nn ");
Exit (1 );
}

Mysql_init (& mysql );
If (! (Sock = mysql_real_connect (& mysql, "localhost", "dbuser", "dbpwd", "9tmd_bbs_utf8", 0, NULL, 0 ))){
Fprintf (stderr, "Couldnt connect to engine! N % snn ", 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, "Couldnt get result from % sn", mysql_error (sock ));
Exit (1 );
}

Printf ("number of fields returned: % dn", mysql_num_fields (res ));

While (row = mysql_fetch_row (res )){
Printf ("Ther userid # % d s username is: % sn", 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
}
When compiling, use the following command

Gcc-o mysql_select. /mysql_select.c-I/usr/local/include/mysql-L/usr/local/lib/mysql-lmysqlclient (-lz) (-lm) the following two options are optional, based on your environment
Run the following command

./Mysql_select 1
The following result is returned:

Number of fields returned: 1
Ther userid #1 s username is: Michael
Query OK!
Most of the above Code can be understood. If you do not understand it, please refer to the C language API documentation provided by MySQL. Each function has a detailed description, when I have time to sort out a common API description