The MySQL structure represents a database connection handle, which contains information about the connection status of the server. Almost all functions use it. To connect to MySQL, you must create a MySQL instance
The MySQL structure represents a database connection handle, which contains information about the connection status of the server. Almost all functions use it. To connect to MySQL, you must create a MySQL instance
If you want to know how to operate databases in C language, you must understand the meanings of these structures. Here is a brief introduction. If you want to learn more deeply, you can search for them on the Internet.
C api data type
1. the MySQL structure represents a database connection handle, which contains information about the connection status of the server. Almost all functions use it. To connect to MySQL, you must create a MySQL instance and initiate the connection through MySQL_init.
2. The MySQL_RES result indicates the returned query result (select, show, etc ). The returned information is also the result set ". In the c API, MySQL_RES is used to read data from the database and MySQL_RES.
3. MySQL_ROW is a type-safe representation of row data. Currently, it is implemented as a string array that counts bytes. (If the field value may contain binary data, you cannot regard it as a null termination string because such a value can contain null bytes internally) rows are obtained by calling MySQL_fetch_row.
The functions available for c api are summarized here. For details, see the MySQL manual.
Function
Description
Mysql_affected_rows ()
Returns the number of rows modified, deleted, or inserted by the last UPDATE, DELETE, or INSERT query.
Mysql_autocommit ()
Switch autocommit mode, ON/OFF
Mysql_change_user ()
Change the user and database on the connection.
Mysql_charset_name ()
Returns the name of the default character set for connection.
Mysql_close ()
Disable the server connection.
Mysql_commit ()
Commit a transaction.
Mysql_connect ()
Connect to the MySQL server. This function is no longer valued and replaced by mysql_real_connect.
Mysql_create_db ()
Create a database. This function is no longer valued and replaced by the SQL statement CREATE DATABASE.
Mysql_data_seek ()
Search for the row number in the query result set.
Mysql_debug ()
Execute DBUG_PUSH with the given string.
Mysql_drop_db ()
Undo the database. This function is no longer valued. Instead, use the SQL statement DROP DATABASE.
Mysql_dump_debug_info ()
Allows the server to write debugging information to logs.
Mysql_eof ()
Determine whether the last row of the result set is read. This function is no longer valued. you can replace it with mysql_errno () or mysql_error.
Mysql_errno ()
Returns the error number of the MySQL function called last time.
Mysql_error ()
Returns the error message of the MySQL function called last time.
Mysql_escape_string ()
Escape special characters for use in SQL statements.
Mysql_fetch_field ()
Returns the type of the next table field.
Mysql_fetch_field_direct ()
If the field number is specified, the type of the table field is returned.
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 ()
Obtain the next row from the result set
Mysql_field_seek ()
Place the column cursor in the specified column.
Mysql_field_count ()
Returns the number of result columns of the last statement executed.
Mysql_field_tell ()
Returns the cursor position of the field used in mysql_fetch_field.
Mysql_free_result ()
Releases the memory used by the result set.
Mysql_get_client_info ()
Returns the Client Version in string format.
Mysql_get_client_version ()
Returns the Client Version Information in integer format.
Mysql_get_host_info ()
Returns the string that describes the connection.
Mysql_get_server_version ()
Returns the server version number in integer format.
Mysql_get_proto_info ()
Returns the Protocol Version Used for the connection.
Mysql_get_server_info ()
Returns the server version number.
Mysql_info ()
Returns information about the latest query.
Mysql_init ()
Obtain or initialize the MYSQL structure.
Mysql_insert_id ()
Returns the ID generated in the previous query for the AUTO_INCREMENT column.
Mysql_kill ()
Kill the specified thread.
Mysql_library_end ()
Finally, determine the MySQL c api library.
Mysql_library_init ()
Initialize 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 the list of current server threads.
Mysql_list_tables ()
Returns the name of the table that matches the simple regular expression.
Mysql_more_results ()
Check whether other results exist.
Mysql_next_result ()
Return/initialize the next result during multi-statement execution.
Mysql_num_fields ()
Number of columns in the returned result set.
Mysql_num_rows ()
The number of rows in the returned result set.
Mysql_options ()
Set connection options for mysql_connect.
Mysql_ping ()
Check whether the connection to the server works and try again if necessary.
Mysql_query ()
Execute an SQL query that is specified as a string ending with Null.
Mysql_real_connect ()
Connect to the MySQL server.
Mysql_real_escape_string ()
Considering the connected Current Character Set, escape special characters in the string to be used in SQL statements.
Mysql_real_query ()
Execute the SQL query specified as the Count string.
Mysql_refresh ()
Refresh or reset the table and cache.
Mysql_reload ()
Notifies the server to load the authorization table again.
Mysql_rollback ()
Roll back the transaction.
Mysql_row_seek ()
Use the value returned from mysql_row_tell () to find the row offset in the result set.
Mysql_row_tell ()
Returns the cursor position of a row.
Mysql_select_db ()
Select a database.
Mysql_server_end ()
Finally, the Embedded Server library is determined.
Mysql_server_init ()
Initialize the Embedded Server library.
Mysql_set_server_option ()
Set options for connection (for example, multiple statements ).
Mysql_sqlstate ()
Returns the SQLSTATE error code about the previous error.
Mysql_shutdown ()
Shut down the database server.
Mysql_stat ()
Returns the server status in string format.
Mysql_store_result ()
Retrieve the complete result set to the client.
Mysql_thread_id ()
Returns the ID of the current thread.
Mysql_thread_safe ()
If the client has been compiled into thread-safe, 1 is returned.
Mysql_use_result ()
Initialize row-by-row result set retrieval.
Mysql_warning_count ()
Returns the number of alerts for the previous SQL statement.
Next, let's take a look at how to use c api to operate databases.
The following example shows how to read data from a database table.