Run a query foreach databases (mysql) - mysql

Question

I'm looking for a straight way to run a query on all databases hosted on my mysql server.
I have a bunch of Magento installations and I want to truncate all Magento log table on all databases:
log_customer
log_visitor
log_visitor_info
log_url
log_url_info
log_quote
report_viewed_product_index
report_compared_product_index
report_event
catalog_compare_item
I think it something very easy to accomplish in mysql but I cannot find a straight answer/solution.
*UPDATE *
According to #Ollie Jones it is not possible to do it without a STORE PROCEDURE or a server side language ( PHP or whatever )
UPDATE 1
I choose to follow the PHP approach (#samitha) for 2 reasons:
STORE PROCEDURE looks more complicated
Query on 'information_schema' table is very slow ( at least if you have many DB/TABLES)

Answer 1

SELECT DISTINCT SCHEMA_NAME AS `database`
FROM information_schema.SCHEMATA
WHERE SCHEMA_NAME NOT IN ('information_schema', 'performance_schema', 'mysql')
ORDER BY SCHEMA_NAME
gets you a list of all the non-MYSQL databases on your system.
SELECT TABLE_SCHEMA AS `database`,
TABLE_NAME AS `table`
FROM information_schema.TABLES
WHERE TABLE_TYPE = 'BASE TABLE'
ORDER BY TABLE_SCHEMA, TABLE_NAME
gets you a list of all the actual tables (excluding SYSTEM VIEWs like the TABLES table, and user-defined views) in all the databases.
Then, you should implement logic in your program to ensure that, for each database, it really is a Magento database before you truncate certain tables. Otherwise, you might become a despised person among your co-workers. :-)
Edit
Here's a stored procedure.
You need to edit it to do exactly what you need it to do; in particular, it counts rows rather than truncating tables, and it doesn't contain the correct list of log tables. (It would be irresponsible for me to publish such a wildly destructive stored procedure; you should edit it yourself to do the destructive part.)
DELIMITER $$
DROP PROCEDURE IF EXISTS `zap_magento_logs`$$
CREATE PROCEDURE `zap_magento_logs`()
BEGIN
-- declare variables for database and table names
DECLARE dbname VARCHAR(128) DEFAULT '';
DECLARE tbname VARCHAR(128) DEFAULT '';
DECLARE done INTEGER DEFAULT 0;
-- declare cursor for list of log tables
DECLARE log_table_list CURSOR FOR
SELECT TABLE_SCHEMA AS `database`,
TABLE_NAME AS `table`
FROM `information_schema`.TABLES
WHERE TABLE_TYPE = 'BASE TABLE'
AND TABLE_NAME IN
(
'log_customer',
'log_visitor',
'log_visitor_info',
'log_url',
'log_url_info',
'log_quote'
)
ORDER BY TABLE_SCHEMA, TABLE_NAME;
-- declare NOT FOUND handler
DECLARE CONTINUE HANDLER
FOR NOT FOUND SET done = 1;
OPEN log_table_list;
log_table: LOOP
FETCH log_table_list INTO dbname, tbname;
IF done = 1 THEN
LEAVE log_table;
END IF;
-- create an appropriate text string for a DDL or other SQL statement
SET #s = CONCAT('SELECT COUNT(*) AS num FROM ',dbname,'.',tbname);
PREPARE stmt FROM #s;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
END LOOP log_table;
CLOSE log_table_list;
END$$
DELIMITER ;
You run this by issuing the SQL command
CALL zap_magento_logs();

Answer 2

A PHP approach would be:
$tables = array(
'log_customer',
'log_visitor',
'log_visitor_info',
'log_url',
'log_url_info',
'log_quote',
'report_viewed_product_index',
'report_compared_product_index',
'report_event',
'catalog_compare_item',
);
$dbh = new PDO('mysql:host=localhost;', 'USERNAME', 'PASSWORD', array(
PDO::ATTR_PERSISTENT => true
));
$sql = $dbh->query('SHOW DATABASES');
$getAllDbs = $sql->fetchALL(PDO::FETCH_ASSOC);
foreach ($getAllDbs as $DB) {
foreach ($tables as $table) {
$dbh->query('TRUNCATE TABLE ' . $DB['Database'] . '.' . $table);
};
};

Answer 3

I didn't feel like writing code to solve this so I found a different solution. I wrote SQL that generates the SQL that I need. So I saved the following to a file called createSomeSQL.sql:
SET sql_mode='PIPES_AS_CONCAT';
select
'truncate table ' || dbs.database || '.someLogTable;'
as ''
from (SELECT DISTINCT SCHEMA_NAME AS `database`
FROM information_schema.SCHEMATA
WHERE SCHEMA_NAME NOT IN ('information_schema', 'performance_schema', 'mysql', 'test')
ORDER BY SCHEMA_NAME) as dbs;
You could replace the SQL in line 4 with anything you want. Then I ran this command to generate the SQL that I need:
mysql -u root -p < createSomeSQL.sql > sqlToExecute.sql
Replace "root" with your username, of course. Now the file sqlToExecute.sql contains a script you can run to execute that SQL against all your databases.

Answer 4

Try the following (very basic, no error handling, may not work at all, I've not tested this):
$db = mysqli_connect(); // your database connection
$tables = ["log_customer", "log_visitor", "log_visitor_info"]; // array with all the tables
foreach ($tables as $table) {
mysqli_query($db, "TRUNCATE TABLE `".$table."`"); // executes query for each element in the array
}