Summary of some common operations on PHP operating MySQL to perform database queries_PHP Tutorial

PHP steps to operate mysql:
1.$connect=mysql_connect('localhost','root','123456') or die('Database connection failed. 'mysql_error());Link mysql.
2.mysql_select_db('database',$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);

Same 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)
For example: filed['id ']=1;
mysql_fetch_row() uses automatically generated numbers (generated sequentially starting from 0) as the key value (that is, the array subscript)
For example: 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 query results of mysql_fetch_assoc() and mysql_fetch_row() into one.
mysql_fetch_object() is similar to 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, but there are two main differences:
1. When connecting, this function will first try to find a server on the same host A (persistent) connection that has already been opened with the same username and password. If found, this connection ID is returned without opening a new connection.
2. Secondly, the connection to the SQL server will not be closed when the script is executed, and 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 recent link of 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 in all fields of 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.
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() Get MySQL host information.

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