MySQL metadata viewing and instance code, mysql metadata

MySQL metadata viewing and instance code, mysql metadata

You may want to know the following information about MySQL:

• Query Result information: number of records affected by SELECT, UPDATE, or DELETE statements.
• Database and data table information: contains the structure information of the database and data table.
• MySQL Server Information: contains the current status and version number of the database server.
  

In the MySQL command prompt, we can easily obtain the above server information. However, if you use Perl, PHP, and other scripting languages, you need to call specific interface functions to obtain them. Next we will introduce in detail.

 Obtain the number of records affected by the query statement.

PERL instance

In the DBI script, the number of records affected by the statement is returned through the do () or execute () function:

# Method 1 # Run $ query my $ count = $ dbh-> do ($ query) using do ); # If an error occurs, 0 printf "% d rows were affected \ n", (defined ($ count )? $ Count: 0); # method 2 # Use prepare () and execute () to execute $ query my $ th = $ dbh-> prepare ($ query ); my $ count = $ something-> execute (); printf "% d rows were affected \ n", (defined ($ count )? $ Count: 0 );

PHP instance

In PHP, you can use the mysql_affected_rows () function to obtain the number of records affected by the query statement.

$ Result_id = mysql_query ($ query, $ conn_id); # returns $ count = ($ result_id? Mysql_affected_rows ($ conn_id): 0); print ("$ count rows were affected \ n ");

Database and data table list

You can easily obtain the list of databases and data tables on the MySQL server. If you do not have sufficient permissions, null is returned.

You can also use the show tables or show databases statement to obtain the list of DATABASES and data TABLES.

PERL instance

# Obtain all available tables in the current database. My @ tables = $ dbh-> tables (); foreach $ table (@ tables) {print "Table Name $ table \ n ";}

PHP instance

 <?php$con = mysql_connect("localhost", "userid", "password");if (!$con){ die('Could not connect: ' . mysql_error());}$db_list = mysql_list_dbs($con);while ($db = mysql_fetch_object($db_list)){ echo $db->Database . "<br />";}mysql_close($con);?> 

Get server metadata

The following command can be used at a MySQL Command Prompt or in a script, such as a PHP script.

Command	Description
Select version ()	Server version information
Select database ()	Current Database Name (or return NULL)
Select user ()	Current User Name
SHOW STATUS	Server Status
SHOW VARIABLES	Server configuration variables

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