[Linux] Ubuntu C language access MySQL database entry, tumysql

[Linux] Ubuntu C language access MySQL database entry, tumysql

The system used is Ubuntu 11. 10. The database is MySQL.

 

MySQL database environment Configuration

 

First, install the MySQL client and server. The command line installation method is as follows:

 

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1. Sudo apt-get install mysql-server mysql-client

Then, to access the database using C programming language, you need to install another development kit:

 

 

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1. Sudo apt-get install libmysqlclient15-dev

 

 

Create a database in MySQL

First, log on to the MySQL database with user rick (the user rick has been granted the root permission to create a database and so on ):

Create a database named foo:

 

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1. Create database foo;

Use the following SQL statement to create a table and insert data:

 

 

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1. Create table children (
2. Childno int (11) not null auto_increment,
3. Fname varchar (30 ),
4. Age int (11 ),
5. Primary key (childno)
6. );
8. Insert into children (childno, fname, age) VALUES (1, 'jenny ', 21 );
9. Insert into children (childno, fname, age) VALUES (2, 'Andrew ', 17 );
10. Insert into children (childno, fname, age) VALUES (3, 'gavin', 8 );
11. Insert into children (childno, fname, age) VALUES (4, 'Duncan ', 6 );
12. Insert into children (childno, fname, age) VALUES (5, 'emma', 4 );
13. Insert into children (childno, fname, age) VALUES (6, 'Alex ', 15 );
14. Insert into children (childno, fname, age) VALUES (7, 'filena', 9 );

Run the following command in MySQL Command Line Mode:

 

 

MySQL database connection test

 

Then use the following C language for database connection test connect1.c:

 

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1. # Include <stdlib. h>
2. # Include <stdio. h>
4. # Include "mysql. h"
6. Int main (int argc, char * argv [])
7. {
8. MYSQL * conn_ptr;
9. Conn_ptr = mysql_init (NULL );
11. If (! Conn_ptr)
12. {
13. Fprintf (stderr, "mysql_init failed \ n ");
14. Return EXIT_FAILURE;
15. }
17. Conn_ptr = mysql_real_connect (conn_ptr, "localhost", "rick", "rick", "foo", 0, NULL, 0 );
19. If (conn_ptr)
20. Printf ("Connection success \ n ");
21. Else
22. Printf ("Connection failed \ n ");
24. Mysql_close (conn_ptr );
26. Return EXIT_SUCCESS;
27. }

Execution result:

 

Note: You need to specify the path name of the include library and library file, and the library module mysqlclient that specifies the link.

If you do not install the SDK at the beginning, the following error occurs:

 

Execute SQL statements for Data Operations

Insert a row to the children database table:

 

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1. # Include <stdlib. h>
2. # Include <stdio. h>
4. # Include "mysql. h"
6. Int main ()
7. {
8. MYSQL my_connecyion;
9. Int res;
11. Mysql_init (& my_connecyion );
13. If (mysql_real_connect (& my_connecyion, "localhost", "rick", "rick", "foo", 0, NULL, 0 ))
14. {
15. Printf ("Connection success \ n ");
17. // Execute the SQL statement
18. Res = mysql_query (& my_connecyion, "insert into children (fname, age) VALUES ('ann ', 3 )");
20. If (! Res)
21. Printf ("Inserted % lu rows \ n", (unsigned long) mysql_affected_rows (& my_connecyion ));
22. Else
23. Fprintf (stderr, "Insert error % d: % s \ n", mysql_errno (& my_connecyion), mysql_error (& my_connecyion ));
25. Mysql_close (& my_connecyion );
26. }
27. Else {
28. Fprintf (stderr, "Connection failed \ n ");
29. If (mysql_errno (& my_connecyion ))
30. Fprintf (stderr, "Connection error % d: % s \ n", mysql_errno (& my_connecyion), mysql_error (& my_connecyion ));
31. }
33. Return EXIT_SUCCESS;
34. }

Running result:

 

 

Note the following:

The mysql_affected_rows function returns the number of rows modified by an update operation, rather than the number of rows that meet the where clause.