The following list summarizes the functions available in the C API. For greater detail, see the descriptions in Chapter 7, C API Function Descriptions.
my_init(): Initializes global variables and the thread handler in thread-safe programs.
mysql_autocommit(): Toggles autocommit mode on/off.
mysql_change_user(): Changes the user and database on an open connection.
mysql_character_set_name(): Returns the default character set name for the current connection.
mysql_client_find_plugin(): Returns a pointer to a plugin.
mysql_client_register_plugin(): Registers a plugin.
mysql_close(): Closes a server connection.
mysql_commit(): Commits the transaction.
mysql_data_seek(): Seeks to an arbitrary row number in a query result set.
mysql_debug(): Does a
DBUG_PUSHwith the given string.
mysql_dump_debug_info(): Causes the server to write debug information to the log.
mysql_errno(): Returns the error number for the most recently invoked MySQL function.
mysql_error(): Returns the error message for the most recently invoked MySQL function.
mysql_escape_string(): Escapes special characters in a string for use in an SQL statement.
mysql_fetch_field(): Returns the type of the next table field.
mysql_fetch_field_direct(): Returns the type of a table field, given a field number.
mysql_fetch_fields(): Returns an array of all field structures.
mysql_fetch_lengths(): Returns the lengths of all columns in the current row.
mysql_fetch_row(): Fetches the next row from the result set.
mysql_field_count(): Returns the number of result columns for the most recent statement.
mysql_field_seek(): Puts the column cursor on a specified column.
mysql_free_result(): Frees memory used by a result set.
mysql_get_character_set_info(): Returns information about default character set.
mysql_get_client_info(): Returns client version information as a string.
mysql_get_client_version(): Returns client version information as an integer.
mysql_get_host_info(): Returns a string describing the connection.
mysql_get_proto_info(): Returns the protocol version used by the connection.
mysql_get_server_info(): Returns the server version number.
mysql_get_server_version(): Returns the server version number as an integer.
mysql_get_ssl_cipher(): Returns the current SSL cipher.
mysql_hex_string(): Encodes a string in hexadecimal format.
mysql_info(): Returns information about the most recently executed query.
mysql_init(): Gets or initializes a
mysql_insert_id(): Returns the ID generated for an
AUTO_INCREMENTcolumn by the previous query.
mysql_kill(): Kills a given thread.
mysql_library_end(): Finalizes the MySQL C API library.
mysql_library_init(): Initializes the MySQL C API library.
mysql_list_dbs(): Returns database names matching a simple regular expression.
mysql_list_fields(): Returns field names matching a simple regular expression.
mysql_list_processes(): Returns a list of the current server threads.
mysql_list_tables(): Returns table names matching a simple regular expression.
mysql_load_plugin(): Loads a plugin.
mysql_load_plugin_v(): Loads a plugin.
mysql_more_results(): Checks whether any more results exist.
mysql_next_result(): Returns/initiates the next result in multiple-result executions.
mysql_num_fields(): Returns the number of columns in a result set.
mysql_num_rows(): Returns the number of rows in a result set.
mysql_ping(): Checks whether the connection to the server is working, reconnecting as necessary.
mysql_plugin_options(): Sets a plugin option.
mysql_query(): Executes an SQL query specified as a null-terminated string.
mysql_real_connect(): Connects to a MySQL server.
mysql_real_escape_string(): Escapes special characters in a string for use in an SQL statement, taking into account the current character set of the connection.
mysql_real_escape_string_quote(): Escapes special characters in a string for use in an SQL statement, taking into account the current character set of the connection and the quoting context.
mysql_real_query(): Executes an SQL query specified as a counted string.
mysql_refresh(): Flushes or resets tables and caches.
mysql_reload(): Tells the server to reload the grant tables.
mysql_reset_connection(): Resets the connection to clear session state.
mysql_rollback(): Rolls back the transaction.
mysql_row_tell(): Returns the row cursor position.
mysql_select_db(): Selects a database.
mysql_server_end(): Finalizes the MySQL C API library.
mysql_server_init(): Initializes the MySQL C API library.
mysql_session_track_get_first(): Gets the first part of session state-change information.
mysql_session_track_get_next(): Gets the next part of session state-change information.
mysql_set_character_set(): Sets the default character set for the current connection.
mysql_set_server_option(): Sets an option for the connection (like
mysql_sqlstate(): Returns the SQLSTATE error code for the last error.
mysql_shutdown(): Shuts down the database server.
mysql_ssl_set(): Prepares to establish an SSL connection to the server.
mysql_stat(): Returns the server status as a string.
mysql_store_result(): Retrieves a complete result set to the client.
mysql_thread_end(): Finalizes a thread handler.
mysql_thread_id(): Returns the current thread ID.
mysql_thread_init(): Initializes a thread handler.
mysql_thread_safe(): Returns 1 if the clients are compiled as thread-safe.
mysql_use_result(): Initiates a row-by-row result set retrieval.
mysql_warning_count(): Returns the warning count for the previous SQL statement.
Application programs should use this general outline for interacting with MySQL:
Initialize the MySQL client library by calling
mysql_library_init(). This function exists in both the
libmysqlclientC client library and the
libmysqldembedded server library, so it is used whether you build a regular client program by linking with the
-libmysqlclientflag, or an embedded server application by linking with the
Issue SQL statements and process their results. (The following discussion provides more information about how to do this.)
Close the connection to the MySQL server by calling
End use of the MySQL client library by calling
The purpose of calling
mysql_library_end() is to provide
proper initialization and finalization of the MySQL client
library. For applications that are linked with the client library,
they provide improved memory management. If you do not call
mysql_library_end(), a block of
memory remains allocated. (This does not increase the amount of
memory used by the application, but some memory leak detectors
will complain about it.) For applications that are linked with the
embedded server, these calls start and stop the server.
In a nonmultithreaded environment, the call to
mysql_library_init() may be
invoke it automatically as necessary. However,
mysql_library_init() is not
thread-safe in a multithreaded environment, and thus neither is
mysql_init(), which calls
mysql_library_init(). You must
prior to spawning any threads, or else use a mutex to protect the
call, whether you invoke
mysql_library_init() or indirectly
mysql_init(). This should
be done prior to any other client library call.
To connect to the server, call
mysql_init() to initialize a
connection handler, then call
mysql_real_connect() with that
handler (along with other information such as the host name, user
name, and password). When you are done with the connection, call
mysql_close() to terminate it. Do
not use the handler after it has been closed.
mysql_real_connect() sets the
reconnect flag (part of the
MYSQL structure) to a value of
0. You can use the
MYSQL_OPT_RECONNECT option to
mysql_options() to control
reconnection behavior. Setting the flag to
cause the client to attempt reconnecting to the server before
giving up if a statement cannot be performed because of a lost
While a connection is active, the client may send SQL statements
to the server using
difference between the two is that
mysql_query() expects the query to
be specified as a null-terminated string whereas
mysql_real_query() expects a
counted string. If the string contains binary data (which may
include null bytes), you must use
SELECT queries, you retrieve
the selected rows as a result set. (Note that some statements are
SELECT-like in that they return
rows. These include
EXPLAIN. Treat these statements the
same way as
There are two ways for a client to process result sets. One way is
to retrieve the entire result set all at once by calling
function acquires from the server all the rows returned by the
query and stores them in the client. The second way is for the
client to initiate a row-by-row result set retrieval by calling
mysql_use_result(). This function
initializes the retrieval, but does not actually get any rows from
In both cases, you access rows by calling
mysql_fetch_row() accesses rows
that have previously been fetched from the server. With
retrieves the row from the server. Information about the size of
the data in each row is available by calling
After you are done with a result set, call
mysql_free_result() to free the
memory used for it.
The two retrieval mechanisms are complementary. Choose the
approach that is most appropriate for each client application. In
practice, clients tend to use
An advantage of
mysql_store_result() is that
because the rows have all been fetched to the client, you not only
can access rows sequentially, you can move back and forth in the
result set using
mysql_row_seek() to change the
current row position within the result set. You can also find out
how many rows there are by calling
mysql_num_rows(). On the other
hand, the memory requirements for
mysql_store_result() may be very
high for large result sets and you are more likely to encounter
An advantage of
is that the client requires less memory for the result set because
it maintains only one row at a time (and because there is less
mysql_use_result() can be faster).
Disadvantages are that you must process each row quickly to avoid
tying up the server, you do not have random access to rows within
the result set (you can only access rows sequentially), and the
number of rows in the result set is unknown until you have
retrieved them all. Furthermore, you must
retrieve all the rows even if you determine in mid-retrieval that
you've found the information you were looking for.
The API makes it possible for clients to respond appropriately to
statements (retrieving rows only as necessary) without knowing
whether the statement is a
You can do this by calling
mysql_store_result() after each
mysql_real_query()). If the result
set call succeeds, the statement was a
SELECT and you can read the rows.
If the result set call fails, call
mysql_field_count() to determine
whether a result was actually to be expected. If
mysql_field_count() returns zero,
the statement returned no data (indicating that it was an
DELETE, and so forth), and was not
expected to return rows. If
mysql_field_count() is nonzero,
the statement should have returned rows, but did not. This
indicates that the statement was a
SELECT that failed. See the
mysql_field_count() for an example
of how this can be done.
mysql_use_result() enable you to
obtain information about the fields that make up the result set
(the number of fields, their names and types, and so forth). You
can access field information sequentially within the row by
repeatedly, or by field number within the row by calling
current field cursor position may be changed by calling
mysql_field_seek(). Setting the
field cursor affects subsequent calls to
mysql_fetch_field(). You can also
get information for fields all at once by calling
For detecting and reporting errors, MySQL provides access to error
information by means of the
mysql_error() functions. These
return the error code or error message for the most recently
invoked function that can succeed or fail, enabling you to
determine when an error occurred and what it was.