C Api--linux Read database contents (MySQL) on C language

To know how to operate the database through the C language, it is necessary to understand the meaning of these several structures, here is simply to say if you want to know more in-depth can be searched online

C API Data type

1, the MySQL structure represents a database connection handle, contains information about the server's connection status, almost all functions are used to him. To connect to MySQL, a MySQL instance must be established and the connection can begin by mysql_init initialization.

2. Mysql_res results represent the returned query results (select,show, etc.). The returned information for the query is also turned into a result set. In the C API, the corresponding is mysql_res, read data from the database, and finally read the data from the Mysql_res。
3, Mysql_rowThis is a type of row data security(Type-safe) 's representation. A string array that is currently implemented as a count byte. (If the field values may contain binary data, you cannot treat these as null-terminated strings, because such values can be obtained by calling the rows that contain empty bytes internally) mysql_fetch_row() .

Here is a summary of the functions that the C API can use, see the MySQL manual

Function	Describe
Mysql_affected_rows ()	Returns the number of rows that were changed/deleted/inserted by the last update, delete, or insert query.
Mysql_autocommit ()	Toggle autocommit mode, ON/off
Mysql_change_user ()	Change the users and databases on the open connection.
Mysql_charset_name ()	Returns the name of the default character set used for the connection.
Mysql_close ()	Close the server connection.
Mysql_commit ()	Commits the transaction.
Mysql_connect ()	Connect to the MySQL server. The function is no longer valued and is replaced with Mysql_real_connect ().
mysql_create_db ()	Create a database. The function is no longer valued, use the SQL statement CREATE database instead.
Mysql_data_seek ()	Finds the attribute row number in the query result set.
Mysql_debug ()	Executes the dbug_push with the given string.
mysql_drop_db ()	Revoke the database. The function is no longer valued, and the SQL statement is used to drop database instead.
Mysql_dump_debug_info ()	Have the server write debug information to the log.
Mysql_eof ()	Determines whether the last row of the result set is read. The function is no longer valued and can be replaced with Mysql_errno () or mysql_error ().
Mysql_errno ()	Returns the error number of the last called MySQL function.
Mysql_error ()	Returns the error message for the last call to the MySQL function.
Mysql_escape_string ()	In order to be used in SQL statements, special characters are escaped.
Mysql_fetch_field ()	Returns the type of the next table field.
Mysql_fetch_field_direct ()	Returns the type of the table field, given the number of fields.
Mysql_fetch_fields ()	Returns an array of all field structures.
Mysql_fetch_lengths ()	Returns the length of all columns in the current row.
Mysql_fetch_row ()	Get the next row from the result set
Mysql_field_seek ()	Places the column cursor in the specified column.
Mysql_field_count ()	Returns the number of result columns for the last executed statement.
Mysql_field_tell ()	Returns the position of the field cursor used by the last Mysql_fetch_field ().
Mysql_free_result ()	Frees the memory used by the result set.
Mysql_get_client_info ()	Returns the client version information as a string.
Mysql_get_client_version ()	Returns the client version information as an integer.
Mysql_get_host_info ()	Returns a string that describes the connection.
Mysql_get_server_version ()	Returns the version number of the server as an integer.
Mysql_get_proto_info ()	Returns the version of the protocol used by the connection.
Mysql_get_server_info ()	Returns the version number of the server.
Mysql_info ()	Returns information about the most recently executed query.
Mysql_init ()	Gets or initializes the MySQL structure.
MYSQL_INSERT_ID ()	Returns the ID of the previous query that was generated for the Auto_increment column.
Mysql_kill ()	Kills a given thread.
Mysql_library_end ()	Finalize the MySQL C API library.
Mysql_library_init ()	Initializes the MySQL C API library.
Mysql_list_dbs ()	Returns the name of the database that matches the simple regular expression.
Mysql_list_fields ()	Returns the name of a field that matches a simple regular expression.
Mysql_list_processes ()	Returns a list of current server threads.
Mysql_list_tables ()	Returns the name of the table that matches the simple regular expression.
Mysql_more_results ()	Check to see if there are other results.
Mysql_next_result ()	Returns/initializes the next result during multi-statement execution.
Mysql_num_fields ()	Returns the number of columns in the result set.
Mysql_num_rows ()	Returns the number of rows in the result set.
Mysql_options ()	Set the connection options for mysql_connect ().
Mysql_ping ()	Check that the connection to the server is working, and reconnect if necessary.
mysql_query ()	Executes a SQL query that is specified as a null-terminated string.
Mysql_real_connect ()	Connect to the MySQL server.
Mysql_real_escape_string ()	Given the current character set of the connection, the special characters in the string are escaped for use in SQL statements.
Mysql_real_query ()	Executes an SQL query that is specified as a count string.
Mysql_refresh ()	Refreshes or resets the table and the high-speed buffer.
Mysql_reload ()	Notifies the server to load the authorization table again.
Mysql_rollback ()	Rolls back the transaction.
Mysql_row_seek ()	Finds the row offset in the result set using the value returned from Mysql_row_tell ().
Mysql_row_tell ()	Returns the row cursor position.
mysql_select_db ()	Select the database.
Mysql_server_end ()	Finalize the embedded server library.
Mysql_server_init ()	Initializes the embedded server library.
Mysql_set_server_option ()	Set options (such as multiple statements) for the connection.
Mysql_sqlstate ()	Returns the SQLSTATE error code for the previous error.
Mysql_shutdown ()	Shut down the database server.
Mysql_stat ()	Returns the server state as a string.
Mysql_store_result ()	Retrieves the complete result set to the client.
MYSQL_THREAD_ID ()	Returns the current thread ID.
Mysql_thread_safe ()	Returns 1 if the client has been compiled for thread-safe.
Mysql_use_result ()	Initializes a row-wise result set retrieval.
Mysql_warning_count ()	Returns the number of alarms for the previous SQL statement.

Here's how you can manipulate the database through the C API.

The following example reads data from a table in a database

#include <stdio.h>
#include <mysql.h>
#include <string.h>
int main ()
{
MySQL MySQL; MySQL Connection
Mysql_res *res; This structure represents a query result set that returns rows
Mysql_row ROW; A representation of the type safety (type-safe) of a row of data
Char *query; Query statements
int t,r;
Mysql_init (&mysql);
if (!mysql_real_connect (&mysql, "localhost", "root", NULL, "test", 0,null,0))
{


printf ("Error Connecting to Database:%s", Mysql_error (&mysql));


}
Else
{
printf ("connected...\n");
}
query= "SELECT * from QQ";
T=mysql_real_query (&mysql,query, (unsigned int) strlen (query));//executes an SQL query that is specified as a count string.
if (t)
{
printf ("Exception occurred when performing display:%s", Mysql_error (&mysql));
}
Res=mysql_store_result (&mysql);//Retrieve the complete result set to the client.
printf ("name \ t School number \ t age \t\n");
while (Row=mysql_fetch_row (res))
{


For (T=0;t<mysql_num_fields (res); t++)
{
printf ("%s\t", row[t]);
}
printf ("\ n");


}
Mysql_free_result (res);//releases the memory used by the result set.
Mysql_close (&mysql);
return 0;
}

Run the following commands and code:

Actually, it's a very simple thing.

C Api--linux Read database contents (MySQL) on C language