Php connection database code Application Analysis

In php, database operations are commonly used. here, code and functions are commonly used in php. The code is as follows:
$ Db_host = 'hostname is database server ';
$ Db_database = 'database name ';
$ Db_username = 'username ';
$ Db_password = 'password ';
$ Connection = mysql_connect ($ db_host, $ db_username, $ db_password); // connect to the database
Mysql_query ("set names 'utf8'"); // Encode and convert
If (! $ Connection ){
Die ("cocould not connect to the database:
". Mysql_error (); // diagnose a connection error
}
$ Db_selecct = mysql_select_db ($ db_database); // select a database
If (! $ Db_selecct)
{
Die ("cocould not to the database
". Mysql_error ());
}
$ Query = "select * from msu"; // Construct a query statement
$ Result = mysql_query ($ query); // execute the query
If (! $ Result)
{
Die ("cocould not to the database
". Mysql_error ());
}
// Array mysql_fetch_row (resource $ result );
While ($ result_row = mysql_fetch_row ($ result) // Retrieve the result and display it
{
$ Num = $ result_row [0];
$ Age = $ result_row [1];
$ Name = $ result_row [2];
Echo"";
Echo"$ Num";
Echo"$ Age";
Echo"$ Name";
Echo"";
}
Mysql_close ($ connection); // close the connection
?>

The code with detailed instructions is as follows:
The code is as follows:
$ Connect = mysql_connect ("127.0.0.1", "root", "") or die ("link error"); // enable link to mysql
$ Select_db = mysql_select_db ("database name", $ connect); // if the connection identifier is not explicitly declared, the last link opened by default
// Execute the SQL statement!
$ SQL = "SELECT * FROM test"
$ Query = mysql_query ($ SQL, $ connect) or die (mysql_error ());

// Difference between the two query functions array/row
$ Row1 = mysql_fetch_row ($ query );
Print_r ($ row1); // only labels in the array can be saved
$ Row2 = mysql_fetch_array ($ query );
Print_r ($ row2); // you can save the labels and field names in the array.
// Loop output while output to an empty position
While ($ row1 ){
Print_r ($ row1 );
}

Mysql_query ("set names 'utf-8 '");

// Calculate the number of query results
Mysql_num_rows ($ query );
// Return the IP address of the last INSERT command
Mysql_insert_id ($ query );
// Obtain the database name
Mysql_tablename ($ query );
// Return error message
Mysql_error ();
// Close the link
Mysql_close ();

PHP connection to mySQL common functions
Mysql can be connected to the web through PHP in two ways, one is Mysql-related functions through php, and the other is ODBC-related functions through php.
The related functions are as follows:
MYSQL functions
Mysql_affected_rows: obtain the number of columns affected by the last MySQL operation.
Mysql_close: disconnect the MySQL server.
Mysql_connect: enables connections to the MySQL server.
Mysql_create_db: create a new MySQL database.
Mysql_data_seek: move internal return indicator.
Mysql_db_query: Send the query string to the MySQL database.
Mysql_drop_db: remove the database.
Mysql_errno: return the error code.
Mysql_error: returns an error message.
Mysql_fetch_array: returns the array data.
Mysql_fetch_field: obtains the field information.
Mysql_fetch_lengths: returns the maximum length of data in each column of a single column.
Mysql_fetch_object: returns object data.
Mysql_fetch_row: returns the columns of a single column.
Mysql_field_name: return the name of the specified field.
Mysql_field_seek: set a field from the indicator to the returned value.
Mysql_field_table: obtain the name of the table in the current column.
Mysql_field_type: obtain the current column type.
Mysql_field_flags: obtains the flag of the current field.
Mysql_field_len: get the length of the current column.
Mysql_free_result: releases the memory occupied by the returned data.
Mysql_insert_id: return the ID of the last INSERT command.
Mysql_list_fields: lists the fields of a specified data table ).
Mysql_list_dbs: list available databases of the MySQL server ).
Mysql_list_tables: lists the tables of a specified database ).
Mysql_num_fields: gets the number of returned fields.
Mysql_num_rows: gets the number of returned columns.
Mysql_pconnect: enables long-term connections to the MySQL server.
Mysql_query: returns a query string.
Mysql_result: Gets the query result.
Mysql_select_db: Select a database.
Mysql_tablename: get the table name.
ODBC functions
To use ODBC functions, you must install MYSQL ODBC
Odbc_autocommit: Enables or disables automatic change.
Odbc_binmode: sets the binary data processing method.
Odbc_close: close the ODBC link.
Odbc_close_all: close all ODBC connections.
Odbc_commit: updates the ODBC database.
Odbc_connect: connect to the ODBC database.
Odbc_cursor: Get the cursor name.
Odbc_do: execute SQL commands.
Odbc_exec: execute SQL commands.
Odbc_execute: execute the preset SQL command.
Odbc_fetch_into: Gets the specified column returned.
Odbc_fetch_row: returns a column.
Odbc_field_name: obtains the column name.
Odbc_field_type: obtains the column data format.
Odbc_field_len: obtains the length of the column data.
Odbc_free_result: refers to the memory used to send data back.
Odbc_longreadlen: sets the maximum value of the return column.
Odbc_num_fields: obtains the number of fields.
Odbc_pconnect: long-term connection to the ODBC database.
Odbc_prepare: preset SQL commands.
Odbc_num_rows: gets the number of returned columns.
Odbc_result: obtain the returned data.
Odbc_result_all: returns HTML table data.
Odbc_rollback: undo the current transaction.
Odbc_setoption: adjusts ODBC settings.