这里有C的API，在C++中也能用
C API Functions
The C API functions are for opening and closing connections to the server, performing queries, analyzing query results, debugging, and performing administrative tasks. You'll need to know them well and know how they interact with the C API data types to master the C API.mysql_affected_rows
my_ulonglong mysql_affected_rows(MYSQL *mysql)
Returns the number of rows affected by the last query (for example, the number of rows removed with a DELETE statement or the number of rows returned from a SELECT statement, in which case it's the same as the mysql_num_rows function.). It returns –1 on error.With UPDATE statements, the row is not counted as affected if it matched the condition but no changes were made, unless the CLIENT_FOUND_ROWS flag is set when connecting with mysql_ real_connect().For example:/* Update the customer table, and return the number of records affected */
mysql_query(&mysql, "UPDATE customer SET first_name='Jackie' WHERE–
surname='Wood')";
affected_rows = mysql_affected_rows(&mysql);
mysql_change_user
my_bool mysql_change_user(MYSQL *mysql, char
*username, char *password, char *database)
Changes the current MySQL user (the one that logged in) to another user (specifying that user's username and password). You can also change database at the same time or open a new connection; otherwise, the current connection and database will be used. This returns true if successful or false if not, in which case the existing user and details are maintained.For example:if (! mysql_change_user(&mysql, 'guru2b', 'g00r002b', 'firstdb')) {
printf("Unable to change user and or database!");
}mysql_character_set_name
char *mysql_character_set_name(MYSQL *mysql)
Returns the name of the default character set (usually ISO-8859-1, or Latin1).For example:printf("The default character set is: %s \n", mysql_character_set_name(&mysql));
mysql_close
void mysql_close(MYSQL *mysql)
Closes the connection and frees the resources.For example:mysql_close(&mysql);
mysql_connect
MYSQL *mysql_connect(MYSQL *mysql, const char *host, const char *user,
const char *passwd)
For connecting to MySQL. The function has been deprecated, so instead use mysql_real_ connect().mysql_create_db
int mysql_create_db(MYSQL *mysql, const char *db)
For creating a database. The function has been deprecated, so instead use mysql_query().mysql_data_seek
void mysql_data_seek(MYSQL_RES *res, unsigned int offset)
Moves the internal row pointer (0 is the first row) associated with the results returned from
mysql_store_result() to a new position. The offset is the row to move to, starting at 0.For example:mysql_data_seek(results, mysql_num_rows(results)-1);
mysql_debug
mysql_debug(char *debug)
To use, the MySQL client needs to have been compiled with debugging enabled. Uses the Fred Fish debug library.For example:/* Traces application activity in the file debug.out */
mysql_debug("d:t:O,debug.out");mysql_drop_db
int mysql_drop_db(MYSQL *mysql, const char *db)
For dropping a database. The function has been deprecated, so instead use mysql_query().mysql_dump_debug_info
int mysql_dump_debug_info(MYSQL *mysql)
Writes connection debug information into the log. The connection needs the SUPER privilege to be able to do this. This returns 0 if it succeeded; otherwise it returns a nonzero result.For example:result = mysql_dump_debug_info(&mysql);
mysql_eof
my_bool mysql_eof(MYSQL_RES *result)
Checks whether the last row has been read. The function has been deprecated, so instead use mysql_err() or mysql_errno().mysql_errno
unsigned int mysql_errno(MYSQL *mysql)
Returns the error code for the most recent API function or 0 if there have been no errors. You can retrieve the actual text of the error using the mysql_error() function.For example:error = mysql_errno(&mysql);
mysql_error
char *mysql_error(MYSQL *mysql)
Returns the error message (in the current server language) for the most recent API function or an empty string if there was no error. If there have been no errors in the connection, the function returns 0.For example:printf("Error: '%s'\n", mysql_error(&mysql));
mysql_escape_string
unsigned int mysql_escape_string(char *to, const char *from, unsigned int length)
Returns a string with all characters that could break the query escaped (a backslash placed before them). Instead, use mysql_real_escape_string() because it respects the current character set. mysql_fetch_field
MYSQL_FIELD *mysql_fetch_field(MYSQL_RES *result)
Returns the field data of the current field. You can call this function repeatedly to return data of the following fields in the result. This returns a null value when there are no more fields to return.
C API Functions
The C API functions are for opening and closing connections to the server, performing queries, analyzing query results, debugging, and performing administrative tasks. You'll need to know them well and know how they interact with the C API data types to master the C API.mysql_affected_rows
my_ulonglong mysql_affected_rows(MYSQL *mysql)
Returns the number of rows affected by the last query (for example, the number of rows removed with a DELETE statement or the number of rows returned from a SELECT statement, in which case it's the same as the mysql_num_rows function.). It returns –1 on error.With UPDATE statements, the row is not counted as affected if it matched the condition but no changes were made, unless the CLIENT_FOUND_ROWS flag is set when connecting with mysql_ real_connect().For example:/* Update the customer table, and return the number of records affected */
mysql_query(&mysql, "UPDATE customer SET first_name='Jackie' WHERE–
surname='Wood')";
affected_rows = mysql_affected_rows(&mysql);
mysql_change_user
my_bool mysql_change_user(MYSQL *mysql, char
*username, char *password, char *database)
Changes the current MySQL user (the one that logged in) to another user (specifying that user's username and password). You can also change database at the same time or open a new connection; otherwise, the current connection and database will be used. This returns true if successful or false if not, in which case the existing user and details are maintained.For example:if (! mysql_change_user(&mysql, 'guru2b', 'g00r002b', 'firstdb')) {
printf("Unable to change user and or database!");
}mysql_character_set_name
char *mysql_character_set_name(MYSQL *mysql)
Returns the name of the default character set (usually ISO-8859-1, or Latin1).For example:printf("The default character set is: %s \n", mysql_character_set_name(&mysql));
mysql_close
void mysql_close(MYSQL *mysql)
Closes the connection and frees the resources.For example:mysql_close(&mysql);
mysql_connect
MYSQL *mysql_connect(MYSQL *mysql, const char *host, const char *user,
const char *passwd)
For connecting to MySQL. The function has been deprecated, so instead use mysql_real_ connect().mysql_create_db
int mysql_create_db(MYSQL *mysql, const char *db)
For creating a database. The function has been deprecated, so instead use mysql_query().mysql_data_seek
void mysql_data_seek(MYSQL_RES *res, unsigned int offset)
Moves the internal row pointer (0 is the first row) associated with the results returned from
mysql_store_result() to a new position. The offset is the row to move to, starting at 0.For example:mysql_data_seek(results, mysql_num_rows(results)-1);
mysql_debug
mysql_debug(char *debug)
To use, the MySQL client needs to have been compiled with debugging enabled. Uses the Fred Fish debug library.For example:/* Traces application activity in the file debug.out */
mysql_debug("d:t:O,debug.out");mysql_drop_db
int mysql_drop_db(MYSQL *mysql, const char *db)
For dropping a database. The function has been deprecated, so instead use mysql_query().mysql_dump_debug_info
int mysql_dump_debug_info(MYSQL *mysql)
Writes connection debug information into the log. The connection needs the SUPER privilege to be able to do this. This returns 0 if it succeeded; otherwise it returns a nonzero result.For example:result = mysql_dump_debug_info(&mysql);
mysql_eof
my_bool mysql_eof(MYSQL_RES *result)
Checks whether the last row has been read. The function has been deprecated, so instead use mysql_err() or mysql_errno().mysql_errno
unsigned int mysql_errno(MYSQL *mysql)
Returns the error code for the most recent API function or 0 if there have been no errors. You can retrieve the actual text of the error using the mysql_error() function.For example:error = mysql_errno(&mysql);
mysql_error
char *mysql_error(MYSQL *mysql)
Returns the error message (in the current server language) for the most recent API function or an empty string if there was no error. If there have been no errors in the connection, the function returns 0.For example:printf("Error: '%s'\n", mysql_error(&mysql));
mysql_escape_string
unsigned int mysql_escape_string(char *to, const char *from, unsigned int length)
Returns a string with all characters that could break the query escaped (a backslash placed before them). Instead, use mysql_real_escape_string() because it respects the current character set. mysql_fetch_field
MYSQL_FIELD *mysql_fetch_field(MYSQL_RES *result)
Returns the field data of the current field. You can call this function repeatedly to return data of the following fields in the result. This returns a null value when there are no more fields to return.
/* .. process results by accessing field->name, field->length etc */
}
mysql_fetch_field_direct
MYSQL_FIELD * mysql_fetch_field_direct(MYSQL_RES * result,–
unsigned int field_number)
Returns field data of the specified field (which starts at 0).For example:/* Return the second field */
field = mysql_fetch_field_direct(results, 1);
mysql_fetch_fields
MYSQL_FIELD *mysql_fetch_fields(MYSQL_RES * result)
Returns an array of field data from each field in the result.For example:unsigned int num_fields;
unsigned int i;
MYSQL_FIELD *fields;/* Returns the number of fields in the result */
num_fields = mysql_num_fields(result);/* Returns an array of field data */
fields = mysql_fetch_fields(result);/* ... Access field data as fields[0].name, fields[1].table and so on */
mysql_fetch_lengths
unsigned long *mysql_fetch_lengths(MYSQL_RES *result)
Returns an array of the lengths of the fields from the current row (called with mysql_fetch_ row()) in the result set, or null if there was an error.This is the only function that correctly returns the length of binary fields (for example, BLOBs). For example:unsigned long *lengths;/* Return the next row of data */
row = mysql_fetch_row(results);/* Return the array of lengths */
length_array = mysql_fetch_lengths(results);/* ... Access lengths as length_array[0], length_array[1] and so on */
mysql_fetch_row
MYSQL_ROW mysql_fetch_row(MYSQL_RES *result)
Returns the next row from the result or null if there are no more rows or an error. For example:MYSQL_ROW row;
row = mysql_fetch_row(results);
/* Access the row data as row[0], row[1] and so on
mysql_field_count
unsigned int mysql_field_count(MYSQL *mysql)
Returns the number of fields in the last executed query. It allows you to determine whether a NULL returned from mysql_use_result() or mysql_store_result() is because of an error or because it shouldn't return a result (a non-SELECT type query). For checking the number of fields in a successful result set, use mysql_num_fields().For example:results = mysql_store_result(&mysql);
/* test if no result set found */
if (results == NULL) {
/* if no result, test whether the field count was zero or not.
if (mysql_field_count(&mysql) > 0) {
/* the query was a SELECT-type, so the null store_result is an error */
}
else {
/* no error, as the query was an INSERT-type, which returns no fields */
}
}
mysql_field_seek
MYSQL_FIELD_OFFSET mysql_field_seek(MYSQL_RES *result, MYSQL_FIELD_OFFSET offset)
Moves the internal field pointer (which starts at 0) to the specified field. The next call to mysql_fetch_field() will the specified field. This returns the previous field position pointer. mysql_field_tell
MYSQL_FIELD_OFFSET mysql_field_tell(MYSQL_RES *result)
Returns the current position of the field pointer.For example:/* Record the current position */
current_pos = mysql_field_tell(results);
mysql_free_result
void mysql_free_result(MYSQL_RES *result)
Frees the resources allocated to a result set.mysql_get_client_info
char *mysql_get_client_info(void)
Returns a string containing the client's MySQL library version.For example:/* Displays - Client library version is: 4.0.2 (for example) */
printf("Client library version is: %s\n", mysql_get_client_info());
mysql_get_host_info
char *mysql_get_host_info(MYSQL *mysql)
Returns a string containing the connection information.For example:/* Displays - Type of connection: Localhost via UNIX socket (for example) */
printf("Type of connection: %s", mysql_get_host_info(&mysql));
mysql_get_proto_info
unsigned int mysql_get_proto_info(MYSQL *mysql)
Returns an integer containing the protocol version (for example, 10) used by the connection. For example:/* displays - Protocol version: 10 (for example) */
printf("Protocol version: %d\n", mysql_get_proto_info(&mysql));
char *mysql_get_server_info(MYSQL *mysql)
Returns a string containing the MySQL server version (for example, 4.0.3).For example:/* displays - Server version: 4.0.3-beta-log (for example) */
printf("Server version: %s\n", mysql_get_server_info(&mysql));mysql_info
char *mysql_info(MYSQL *mysql)
Returns a string containing detailed information about the most recent query. Detailed information includes records, rows matched, changes, and warnings.For example:/* Query info String format: Rows matched: 19 Changed: 19 Warnings: 0
(for example) */
printf("Query info: %s\n", mysql_info(&mysql));
mysql_init
MYSQL *mysql_init(MYSQL *mysql)
Returns an initialized MySQL handle, ready for a mysql_real_connect(). The argument can be a null pointer, in which case a structure will be created, or a pointer to an existing MYSQL structure. The mysql_close() function frees the resources from the structure if it created it. If you passed an existing structure, you'll need to free the resources yourself after the connection is closed.mysql_insert_id
my_ulonglong mysql_insert_id(MYSQL *mysql)
Returns a value containing the most recently inserted AUTO_INCREMENT value or 0 if the most recent query did insert an auto incremented value.For example:last_auto_increment = mysql_insert_id(&mysql);
mysql_kill
int mysql_kill(MYSQL *mysql, unsigned long process_id)
Requests that MySQL kill the thread specified by the process_id. This returns 0 if operation was successful or a nonzero value if it failed.Requires that you have the PROCESS privilege.For example:kill = mysql_kill(&mysql, 1293);
mysql_list_dbs
MYSQL_RES *mysql_list_dbs(MYSQL *mysql, const char *wild)
Returns a result set containing the names of the databases on the server that match the wild regular expression (equivalent to the SQL statement SHOW DATABASES LIKE 'wild') or null if there was an error. This returns all databases if passed a null pointer. For example:MYSQL_RES database_names;/* returns a list of all databases with 'db' in the name */
database_names = mysql_list_dbs(&mysql, "%db%");/* ... Don't forget to free the resources at a later stage
mysql_free_result(database_names);
mysql_list_fields
MYSQL_RES *mysql_list_fields(MYSQL *mysql, const char *table, const char *wild)
Returns a result set containing the names of the fields in the specified table that match the wild regular expression (equivalent to the SQL statement SHOW COLUMNS FROM tablename LIKE 'wild') or null if there was an error. This returns all fields if passed a null pointer.For example:MYSQL_RES field_names;/* returns a list of all fields with 'name' in the name */
field_names = mysql_list_fields(&mysql, "customer", "%name%");/* ... Don't forget to free the resources at a later stage
mysql_free_result(field_names);
mysql_list_processes
MYSQL_RES *mysql_list_processes(MYSQL *mysql)
Returns a result set containing a description of the currently running database server threads or null if there was an error. Returns the same information as returned through the SHOW PROCESSLIST statement (that is, the process ID, username, hostname, database, action, time, state, and info). You can then as usual pass the result to mysql_fetch_row() to access the results.For example:MYSQL_RES *threadlist;
MYSQL_ROW row
threadlist = mysql_list_processes(&mysql);
row = mysql_fetch_row(threadlist);
/* Access the thread data as row[0], row[1] and so on/* ... Don't forget to free the resources at a later stage
mysql_free_result(threadlist);
mysql_list_tables
MYSQL_RES *mysql_list_tables(MYSQL *mysql, const char *wild)Returns a result set containing the names of the tables in the current database that match the wild regular expression (equivalent to the SQL statement SHOW TABLES LIKE 'wild') or null if there was an error. This returns all fields if passed a null pointer.For example:MYSQL_RES tablelist;/* returns a list of all tables with 'customer' in the name */
tablelist = mysql_list_tables(&mysql, "%customer%");/* ... Don't forget to free the resources at a later stage
mysql_free_result(tablelist);
mysql_num_fields
unsigned int mysql_num_fields(MYSQL_RES *result)
Returns the number of fields in the query result. Use the mysql_field_count() function to check for errors, and use this function to check number of fields in a successful result set.For example:num_fields = mysql_num_fields(results);
mysql_num_rows
int mysql_num_rows(MYSQL_RES *result)
Returns the number of rows in a query result (only the results to date if mysql_use_result() was used to get the result set).For example:num_rows = mysql_num_rows(results);
mysql_options
int mysql_options(MYSQL *mysql, enum mysql_option option, void *value)
Sets extra connect options for the connection about to be made. It can be called multiple times and is called after mysql_init() and before mysql_real_connect(). This returns 0 if successful or a nonzero value if it was passed an invalid option. The options are as follows:MYSQL_OPT_CONNECT_TIMEOUT An unsigned int *, specifies the connect timeout in seconds.MYSQL_OPT_COMPRESS Uses the compressed client/server protocol.MYSQL_OPT_LOCAL_INFILE An optional pointer to uint. LOAD DATA LOCAL is enabled if the pointer points to nonzero unsigned integer or none is supplied.MYSQL_OPT_NAMED_PIPE On Windows NT, uses named pipes to connect to the server.MYSQL_INIT_COMMAND A char *, specifies a query to run as soon as the connection is established (including an automatic reconnection). MYSQL_READ_DEFAULT_FILE A char *, causes the options to be from the name file, instead of the usual configuration file (my.cnf or my.ini).MYSQL_READ_DEFAULT_GROUP A char *, causes the options to be read from the named group inside the configuration file (my.cnf or my.ini, or as set by MYSQL_READ_DEFAULT_ FILE).For example:MYSQL mysql;
mysql_init(&mysql);/* use compression, and flush the tables upon connecting */
mysql_options(&mysql, MYSQL_OPT_COMPRESS, 0 );
mysql_options(&mysql, MYSQL_INIT_COMMAND, "FLUSH TABLES" );/* ... continue and connect */
if(!mysql_real_connect(&mysql, "localhost", "guru2b", "g00r002b",–
"firstdb", 0,NULL,0)) {
printf("The following connection error occurred %s\n",
mysql_error(&mysql));
}
mysql_ping
int mysql_ping(MYSQL *mysql)
Returns 0 if the MySQL server is up or a nonzero value if not. If the ping fails, the program will try to reconnect.mysql_query
int mysql_query(MYSQL *mysql, const char *query)
Performs the specified query. It returns 0 if successful or a nonzero value if there was an error. To perform a query with binary data (which could contain the null character), you need to use
mysql_real_query() instead. You should use this function for dropping and creating databases as well, replacing the deprecated mysql_create_db() and mysql_drop_db() functions.You can then retrieve the result, if applicable, with the mysql_store_result() or mysql_use_result() functions.For example:query_result = mysql_query(&mysql, "CREATE DATABASE seconddb");
一定是我描述的不太清楚，我现在求教的是如何用c/c++（两者均可）访问数据库，我现在第一步都不能实现，我不能连接上服务器上的mysql数据库阿。两位可有源码给个例子阿？我现在一头雾水，郁闷ing...
MYSQL* mysql;
mysql = mysql_init(NULL);
if(mysql == NULL)
{
printf("init mysql failed\n");
return DB_ERROR;
}
if (mysql_real_connect(mysql, "localhost", "username","yourpasswd","dbname",0, NULL, CLIENT_FOUND_ROWS) == NULL)
{
printf("Failed to connect to database: Error: %s\n", mysql_error(mysql)); mysql_close(mysql);
mysql = NULL;
return DB_ERROR;
}............. MYSQL_RES *result;
if (mysql_query(mysql, "select * from table_name") == 0)
{
result = mysql_store_result(mysql);
m_nAffectedRows = (long)mysql_affected_rows(mysql);
if (result == NULL)
{
printf("no record");
}
else
{
MYSQL_ROW row;
row = mysql_fetch_row(result);
}
}
else
printf("query error\n");另外要确认/usr/lib/目录下存在libmysqlclient.so文件
MYSQL* mysql;
mysql = mysql_init(NULL);
if(mysql == NULL)
{
printf("init mysql failed\n");
return DB_ERROR;
}
if (mysql_real_connect(mysql, "localhost", "username","yourpasswd","dbname",0, NULL, CLIENT_FOUND_ROWS) == NULL)
{
printf("Failed to connect to database: Error: %s\n", mysql_error(mysql)); mysql_close(mysql);
mysql = NULL;
return DB_ERROR;
}............. MYSQL_RES *result;
if (mysql_query(mysql, "select * from table_name") == 0)
{
result = mysql_store_result(mysql);
m_nAffectedRows = (long)mysql_affected_rows(mysql);
if (result == NULL)
{
printf("no record");
}
else
{
MYSQL_ROW row;
row = mysql_fetch_row(result);
}
}
else
printf("query error\n");另外要确认/usr/lib/目录下存在libmysqlclient.so文件
可是编译的时候有很多的错误阿
说mysql_com.h文件中有错误，总之编译都过不去阿
就是没法用MYSQL *****
您是怎么解决的阿？