Steps and methods to execute mysql query in php

This article introduces some methods of querying the MySQL database in PHP and the differences between them. Friends in need can refer to them.

Steps for php to operate mysql:

1. $connect=mysql_connect('localhost','root','123456') or die('Database connection failed.'mysql_error()); Link to mysql. 2. mysql_select_db('database',$connect) selects the linked database. 3. mysql_query('Set names gb2312'); $sql = "select * from blog_article"; Prepare the data to be queried. 4. $datas = mysql_query($sql); execute sql query. 5. $data = mysql_fetch_assoc($datas) gets the queried piece of data cached in memory. 6.print_r($data);

Similar points: The three functions all return a row of data queried in the database (to put it more clearly, it is a row of data).

Difference: mysql_fetch_assoc() uses the corresponding field name in the database as the key value (that is, the array subscript), such as: filed['id']=1;

mysql_fetch_row() uses automatically generated numbers (generated sequentially starting from 0) as the key value (that is, the array subscript) such as: filed[0]=1;

mysql_fetch_array() uses automatically generated numbers (generated sequentially starting from 0) as the key value (that is, the array subscript), and it also generates the corresponding field name in the database as the key value (that is, the array subscript) (standard) such as: filed[0]=1, filed['id']=1; that is to say, mysql_fetch_array() combines the results of mysql_fetch_assoc() and mysql_fetch_row() into one.

mysql_fetch_object() is almost the same as mysql_fetch_assoc(). It's just that mysql_fetch_assoc() returns an array. mysql_fetch_object() returns the object object. mysql_insert_id() gets the ID generated by the previous INSERT operation. The mysql_result() function returns the value of a field in the result set. The mysql_num_fields() function returns the number of fields in the result set. mysql_affected_rows();Returns the number of record rows affected by the previous MySQL operation. mysql_num_rows(mysql_query($sql)) gets the number of rows in the result set. The mysql_pconnect() function opens a persistent connection to the MySQL server.

mysql_pconnect() and mysql_connect() are very similar, the main differences are: 1. When connecting, this function will first try to find a (persistent) connection that has been opened on the same host with the same user name and password. If found, the connection ID will be returned without opening a new connection. 2. Secondly, the connection to the SQL server will not be closed when the script completes execution, the connection will remain open for future use (mysql_close() will not close the connection established by mysql_pconnect()).

mysql_data_seek(mysql_query($sql),8); Get the 8th piece of data in the result set. (mysql_num_rows(mysql_query($sql)) and mysql_data_seek(mysql_query($sql),8) cannot be used in mysql_unbuffered_query($sql).) mysql_unbuffered_query($sql) and mysql_query($sql) have similar effects, but mysql_unbuffered_query($sql) does not cache. mysql_query($sql) will cache the query results. mysql_close(); Close the latest link to mysql. mysql_field_flags(mysql_query($sql),6) returns the table attribute output of the sixth field such as: not_null.

primary_key auto_increment . mysql_fetch_lengths(mysql_query($sql)) returns the length of each field of all fields in the data. What is returned is an array of numbers. mysql_field_name(mysql_query($sql),3) returns the field name of the third field. mysql_field_table(mysql_query($sql),0) returns the table name where the specified field is located. The mysql_free_result(mysql_query($sql)) function releases the result memory. The mysql_get_client_info() function returns MySQL client information. mysql_get_host_info() Gets MySQL host information.