TRUNCATE all tables matching name pattern - mysql

Question

This is the sql i'm using based from this answer:
SET #pattern = '%_movielist';
SELECT concat('TRUNCATE TABLE ', GROUP_CONCAT(concat(TABLE_NAME)), ';')
INTO #truncatelike FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_NAME LIKE #pattern;
SELECT #truncatelike;
PREPARE stmt FROM #truncatelike;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
but I get this error Access denied for user 'root'#'%' to database 'information_schema'.
What am I doing wrong? It seems to work for other users

Answer 1

You trying to execute this statement on "information_schema" database. Read more about this database [https://dev.mysql.com/doc/refman/5.7/en/information-schema.html]
You should not be running statements on the information_schema database (unless you REALLY know what you're doing). The database serves as a "meta" repository that dictates how the server operates. Chances are that you have no need to touch it and you'll likely brick your server if you do.
This is already answered here. [#1044 - Access denied for user 'root'#'localhost' to database 'information_schema'
Restriction to above: This query will work only if the no of table returned by the statement is 1 for more than 1 tables, you will require to use it in iteration.
To make this work for all the table matching the pattern we would require to use stored procedure.
Please change the Procedure name
CREATE PROCEDURE `new_procedure`()
BEGIN
-- Pattern to Match
SET #pattern = '%_movielist';
-- Temporary Table to Store the Result of The Select Statement
CREATE TEMPORARY TABLE IF NOT EXISTS Table_ToBeTruncated
(
Id int NOT NULL AUTO_INCREMENT,TableName varchar(100),
PRIMARY KEY (id)
);
-- Insert all the TableName to be Truncated
insert Table_ToBeTruncated(TableName)
SELECT distinct concat('TRUNCATE TABLE `', TABLE_NAME, '`;')
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_NAME LIKE #pattern and TABLE_SCHEMA = 'movielist';
-- Declare a variable to count the no of records to be truncated.
SET #count=(Select count(*)from Table_ToBeTruncated);
-- Iterate the list
WHILE #count> 0 DO
-- Pick One table from the Temporary Table List;
SELECT TableName into #truncatelike from Table_ToBeTruncated where ID= #count;
-- Prepare the statement
PREPARE stmt FROM #truncatelike;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
-- Decrease the counter.
set #count = #count- 1;
END WHILE;
drop TEMPORARY TABLE IF EXISTS Table_ToBeTruncated ;
END