Several common database operation functions in MySQL

Some common MYSQL operation functions are closely related to MYSQL operations. I believe they will be of great help to beginners of PHP development.

1. mysql_connect -- open a link to the MySQL server

Note: The link is closed after the page is executed.

Example:

$ Link = mysql_connect ("localhost", "root", "") or die ("cocould not connect:". mysql_error ());

2. mysql_close -- close the MySQL Link

Function Format: bool mysql_close ([resource link_identifier])

Note: link_identifier closes the last non-persistent link by default.

Example:

$ Link = myql_connect ("localhost", "root", "") or die ("link failed! Error message: ". mysql_error ());

Echo "link successful ";

Mysql_close ($ link );?

3. mysql_pconnect -- open an execution link to the MySQL server

Note: similar to mysql_connect, only persistent links are established, which is more common and convenient.

Example:

$ Link = mysql_pconnect ("localhost", "root", "") or die ("cocould not connect:". mysql_error ());

4. mysql_select_db -- select MySQL database

Function Format: bool mysql_select_db (string database_name, resource link_identifier)

Note: after the connection is successful, you should immediately use this function to specify a database for the link identifier.

Example:

$ Link = myql_connect ("localhost", "root", "") or die ("link failed! Error message: ". mysql_error (); echo" link successful ";

Mysql_select_db ("example", $ link) or die ('unable to use example database ');

Mysql_query ("insert into users (name) values ('zhang san ')");

Mysql_close ($ link );

5. mysql_query -- send a MySQL statement

Note: This is the most common function. It is used to execute almost all SQL statements and MySQL-specific commands.

Function Format: resource mysql_query (string query, resource link_identifier)

Example:

$ Result = mysql_query ("SELECT * FROM users ");

6. mysql_num_rows -- get the number of rows in the result set

Function Format: int mysql_rows (resource result)

Description: gets the number of records in the result set, which is only valid for the result set returned by SELECT. For UPDATE/INSERT Results, use the mysql_affected_rows function to obtain the number of affected records.

Example:

$ Result = my example SQL _query ("SELECT * FROM users", $ link );

$ Num_rows = mysql_num_rows ($ result );

Echo "found". $ num_rows. "record \ n ";

7. mysql_affected_rows -- obtain the number of records affected by the previous MySQL operation

Function Format: int mysql_affected_rows (resource link_identifier)

Note: This function should be executed immediately after the corresponding SQL mysql_query function is executed.

Example:

Mysql_query ("delete from users WHERE id <10 ");

Echo "this operation deleted". mysql_affected_rows (). "Row record ";

8. mysql_error -- return the text error message generated by the previous MySQL operation

Function Format: string mysql_error (resource link_identifier)

Description: it returns the text of the last MySQL error.

9. mysql_insert_id -- get the ID generated by the previous INSERT operation

Function Format: int mysql_insert_id (resource link_identifier)

Description: used to obtain the primary key value automatically generated by MySQL during the last INSERT operation.

Example:

Mysql_query ("insert into users (name) values ('kossu ')");

Echo ("id of the last insert operation". mysql_insert_id ());

10. mysql_fetch_array -- get a row from the result set as an associated array, or an array of numbers, or both

Function Format: array mysql_fetch_array (resource result, int result_type)

Note: retrieve a record from the result set in the form of an array and move down a cursor. Through this array, you can access the target data.

Parameter description: result: The result set obtained through the mysql_query function.

Result_type: it can only be MYSQL_ASSOC, MYSQL_NUM, or MYSQL_BOTH, which indicates the array index format is returned. The default value is MYSQL_BOTH.

Example:

$ Result = mysql_query ("SELECT id, name FROM users ");

While ($ row = mysql_fectch_array ($ result ))

{

Echo "id =". $ row [0]. "; name =". $ row ["name"]."

";

}

With reference to these functions, you can write a PHP-based MYSQL operation class, which includes MYSQL connection, link closure, data deletion, modification, and content addition.