We are cleaning our MySQL database and finding many rows with empty string (as value) in ENUM columns. MySQL has the nasty habit of ignoring errors like that, you know.
So, since we have hundreds of tables, I was wondering if there is a way to find which tables have this problem. Solutions involving queries, procedures or phpMyAdmin commands are welcome.
Thanks in advance!
P.S. My first question here! Yay!
So, following the suggestions in the comments, I made a procedure that prints the table name, the column name and the number of rows with empty strings instead of a ENUM value.
It works in mysql terminal app, but not in phpMyAdmin.
USE __DATABASE_NAME_HERE__;
DELIMITER //
DROP PROCEDURE IF EXISTS hunt //
CREATE PROCEDURE hunt()
BEGIN
DECLARE done INT DEFAULT false;
DECLARE current_table_name VARCHAR(255);
DECLARE current_column_name VARCHAR(255);
DECLARE my_cursor CURSOR FOR
SELECT table_name, column_name
FROM information_schema.columns
WHERE information_schema.columns.table_schema = "__DATABASE_NAME_HERE__" AND information_schema.columns.column_type LIKE "%ENUM%";
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
OPEN my_cursor;
my_loop: LOOP
FETCH my_cursor INTO current_table_name, current_column_name;
IF done THEN
LEAVE my_loop;
END IF;
SET #sql = CONCAT(
' SELECT COUNT(*) as column_count, "', current_table_name, '" AS table_name, "', current_column_name, '" AS column_name',
' FROM ', current_table_name,
' WHERE `', current_column_name , '` = ""',
' HAVING column_count > 0'
);
PREPARE stmt FROM #sql;
EXECUTE stmt;
DROP PREPARE stmt;
END LOOP;
CLOSE my_cursor;
END //
DELIMITER ;
CALL hunt();
Related
I have to send comma separated values into a select statement where it will update values through #sql statement.
I have common table in all Databases I need to update the table column by one update statement in the procedure.
For Example : Input Param will be ('DataBase1','Database2',....., 'Database10')
Below is the sample procedure :
DELIMITER &&
CREATE PROCEDURE update_stmt (IN DBName varchar(100))
BEGIN
Declare DBName = #DB;
**comma seperated values loop and placed into the #DB**
use #DB;
SELECT concat(update #DB.sample SET COL = 0 where ID = \'',ID,'\','; ) as stmt FROM
Test.Sample into #s;
SET #sql = #s
PREPARE stmt from #sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
END &&
DELIMITER ;
so that update statement will execute in each of the databases.
Here's another approach. I don't try to split the comma-separated string, I use it with FIND_IN_SET() to match schema names in INFORMATION_SCHEMA.TABLES. This filters to schemas in the list that actually exist, and tables that actually exist in that schema.
Then use a cursor to loop over the matching rows, so you don't have to split any strings, which is awkward to do in a stored procedure.
I supposed that you would want to specify the id of the row to update too, so I added that to the procedure parameters.
Also notice the use of quotes when I create #sql. You can concatenate strings, but those must be quote-delimited like any other string literal. Variables must not be inside the quoted string. There's no feature to expand variables inside string literals in MySQL.
DELIMITER &&
CREATE PROCEDURE update_stmt (IN schema_name_list VARCHAR(100), IN in_id INT)
BEGIN
DECLARE done INT DEFAULT false;
DECLARE schema_name VARCHAR(64);
DECLARE cur1 CURSOR FOR
SELECT TABLE_SCHEMA FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_NAME = 'sample' AND FIND_IN_SET(TABLE_SCHEMA, schema_name_list);
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = true;
SET #id = in_id;
OPEN cur1;
schema_loop: LOOP
FETCH cur1 INTO schema_name;
IF done THEN
LEAVE schema_loop;
END IF;
SET #sql = CONCAT('UPDATE `', schema_name, '`.sample SET col = 0 WHERE id = ?');
PREPARE stmt FROM #sql;
EXECUTE stmt USING #id;
DEALLOCATE PREPARE stmt;
END LOOP;
CLOSE cur1;
END &&
DELIMITER ;
Frankly, I hardly ever use stored procedures in MySQL. The procedure language is primitive, and the tasks I see people try to do in stored procedures could be done a lot more easily in virtually every other programming language.
I have a mysql database with about 8 tables that all begin with a capital letter. Any quick way to lowercase them all? Or even one by one... if i try this, RENAME TABLE Contacts TO contacts it says ERROR 1050 (42S01): Table 'contacts' already exists
Use two renames - first to a temp name and then to the lowercased:
RENAME TABLE Contacts TO contacts_
and then
RENAME TABLE contacts_ TO contacts
Of course, you should be careful not to try using an already existing table name, but if you initially had tables 'Contacts' and 'contacts_' I'd say you have way more serious problems than the case.
By checking this link, you have to:
RENAME TABLE tbl_name TO new_tbl_name
BUT : The new_tbl_name must NOT be used by another table as the name must be unique
I'm sorry for bringing back an old post. But I had problems with this aswell.
I made this function to automate the above. I didn't help in my case, but might help other people. That's why I'm posting it here.
DELIMITER $$
CREATE DEFINER=`root`#`localhost` PROCEDURE `lowercasetables`()
BEGIN
DECLARE done INT DEFAULT 0;
DECLARE tempname varchar(255);
DECLARE backupname varchar(255);
DECLARE sqlst varchar(5000);
DECLARE cur1 CURSOR FOR SELECT table_name FROM information_schema.TABLES where table_schema = schema();
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;
OPEN cur1;
REPEAT
FETCH cur1 INTO tempname;
SET backupname = concat(tempname,'_BACKUP');
SET #sqlst = CONCAT(CONCAT('RENAME TABLE ', tempname), CONCAT(' TO ', backupname));
PREPARE stmt1 FROM #sqlst;
EXECUTE stmt1;
DEALLOCATE PREPARE stmt1;
SET #sqlst = CONCAT(CONCAT('RENAME TABLE ', backupname), CONCAT(' TO ', LOWER(tempname)));
PREPARE stmt2 FROM #sqlst;
EXECUTE stmt2;
DEALLOCATE PREPARE stmt2;
UNTIL done END REPEAT;
CLOSE cur1;
END
Seen a lot for dropping tables using a wildcard but not a direct SQL statement except this one:
http://azimyasin.wordpress.com/2007/08/11/mysql-dropping-multiple-tables/
It says:
SHOW TABLES LIKE ‘phpbb_%’;
then DROP TABLES, is there a neat way to combine this all into one SQL Statement?
You could use dynamic SQL to do it, inside a stored procedure. It'd look something like this (untested):
CREATE PROCEDURE drop_like (IN pattern VARCHAR(64))
BEGIN
DECLARE q tinytext;
DECLARE done INT DEFAULT FALSE;
DECLARE cur CURSOR FOR
SELECT CONCAT('DROP TABLE "', table_schema, '"."', table_name, '"')
FROM information_schema.tables WHERE table_type = 'BASE TABLE' AND table_name LIKE pattern;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
OPEN cur;
drop_loop: LOOP
FETCH cur INTO q;
IF done THEN
LEAVE drop_loop;
END IF;
PREPARE stmt FROM #q;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
END LOOP;
CLOSE cur;
END;
Using dynamic SQL in a query, as per derobert's answer, is the only to do this with pure SQL (no app code).
I wrote a generalized procedure to do this sort of thing (run a query for every table in a database) that you can find here - to use it, you would just need to run this query:
CALL p_run_for_each_table('databasename', 'DROP TABLE `{?database}`.`{?table}`');
It works in essentially the same way as derobert's answer.
However, the writer of that blog post was probably expecting you to write app code to turn the names of tables into a single DROP statement.
To do this, you would iterate over the results of the SHOW TABLE in your code and build a single query like this:
DROP TABLE table1, table2, tablewhatever;
This can be achieved via stored procedure, for example:
CREATE DEFINER=`some_user`#`%` PROCEDURE `drop_tables`()
LANGUAGE SQL
NOT DETERMINISTIC
MODIFIES SQL DATA
SQL SECURITY DEFINER
COMMENT ''
BEGIN
#We need to declare a variable with default 0 to determine weather to continue the loop or exit the loop.
DECLARE done INT DEFAULT 0;
DECLARE archive_table_name VARCHAR(100);
#Select desired tables from `information_schema`
DECLARE cur CURSOR FOR
SELECT t.`TABLE_NAME` FROM information_schema.`TABLES` t WHERE t.`TABLE_NAME` LIKE 'some_table_name%'
AND t.CREATE_TIME BETWEEN DATE_SUB(NOW(), INTERVAL 9 MONTH) AND DATE_SUB(NOW(), INTERVAL 6 MONTH);
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;
OPEN cur;
read_loop: LOOP
#Fetch one record from CURSOR and set variable (if not found, then variable `done` will be set to 1 by continue handler)
FETCH cur INTO archive_table_name;
IF done THEN
LEAVE read_loop; #If done is set to 1, then exit the loop, else continue
END IF;
#Do your work
-- Create the truncate query
SET #s = CONCAT('DROP TABLE IF EXISTS ', archive_table_name);
-- Prepare, execute and deallocate the truncate query
PREPARE drop_statement FROM #s;
EXECUTE drop_statement;
DEALLOCATE PREPARE drop_statement;
END LOOP;
CLOSE cur; #Closing the cursor
END
Pay attention to the database user, which is creating/executing the stored routine: it must have appropriate credentials for executing/dropping tables.
I'm performing some database clean up and have noticed that there are a lot of columns that have both empty strings and NULL values in various columns.
Is it possible to write an SQL statement to update the empty strings to NULL for each column of each table in my database, except for the ones that do not allow NULL's?
I've looked at the information_schema.COLUMNS table and think that this might be the place to start.
It's not possible to do this with one simple SQL statement.
But you can do it using one statement for each column.
UPDATE TABLE SET COLUMN = NULL
WHERE LENGTH(COLUMN) = 0
or, if you want to null out the items that also have whitespace:
UPDATE TABLE SET COLUMN = NULL
WHERE LENGTH(TRIM(COLUMN)) = 0
I don't think it's possible within MySQL but certainly with a script language of your choice.
Start by getting all tables SHOW TABLES
Then for each table get the different columns and find out witch ones allow null, either with DESC TABLE, SHOW CREATE TABLE or SELECT * FROM information_schema.COLUMNS, take the one you rather parse
Then for each column that allows null run a normal update that changes "" to null.
Prepare to spend some time waiting :)
I figured out how to do this using a stored procedure. I'd definitely look at using a scripting language next time.
DROP PROCEDURE IF EXISTS settonull;
DELIMITER //
CREATE PROCEDURE settonull()
BEGIN
DECLARE done INT DEFAULT FALSE;
DECLARE _tablename VARCHAR(255);
DECLARE _columnname VARCHAR(255);
DECLARE cur1 CURSOR FOR SELECT
CONCAT(TABLE_SCHEMA, '.', TABLE_NAME) AS table_name,
COLUMN_NAME AS column_name
FROM information_schema.COLUMNS
WHERE IS_NULLABLE = 'YES'
AND TABLE_SCHEMA IN ('table1', 'table2', 'table3');
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
OPEN cur1;
read_loop: LOOP
FETCH cur1 INTO _tablename, _columnname;
IF done THEN
LEAVE read_loop;
END IF;
SET #s = CONCAT('UPDATE ', _tablename, ' SET ', _columnname, ' = NULL WHERE LENGTH(TRIM(', _columnname, ')) = 0' );
PREPARE stmt FROM #s;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
END LOOP;
CLOSE cur1;
END//
DELIMITER ;
CALL settonull();
I have a joomla mysql database with a table name prefix of "jos_" on all of my table names. But I would like to remove it from all of my tables. I understand how to rename each table, one at a time, but I have 600 tables. Is there an easy to run a sql query to do this.
If someone has a solution, could you please post the exact sql query I can use?
In phpmyadmin select all tables of your database.
From the dropdown 'With selected:' choose 'Replace table prefix'
Set from->to replacement.
DONE
You can generate the necessary statements with a single query:
select 'RENAME TABLE ' || table_name || ' TO ' || substr(table_name, 5) ||';'
from information_schema.tables
Save the output of that query to a file and you have all the statements you need.
Or if that returns 0s and 1s rather the statemenets, here's the version using concat instead:
select concat('RENAME TABLE ', concat(table_name, concat(' TO ', concat(substr(table_name, 5), ';'))))
from information_schema.tables;
You can create your own stored procedure to rename your tables, with that you don't need to open an external editor everything will be done on the server:
delimiter //
CREATE PROCEDURE rename_tables( IN db CHAR(255), IN srch CHAR(255), IN rplc CHAR(255) )
BEGIN
DECLARE done INT DEFAULT 0;
DECLARE from_table CHAR(255);
DECLARE cur1 CURSOR FOR SELECT TABLE_NAME FROM information_schema.TABLES WHERE TABLE_SCHEMA=db;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;
OPEN cur1;
read_loop: LOOP
IF done THEN
LEAVE read_loop;
END IF;
FETCH cur1 INTO from_table;
SET #to_table = REPLACE(from_table, srch, rplc);
IF from_table != #to_table THEN
SET #rename_query = CONCAT('RENAME TABLE ', db, '.', from_table, ' TO ', #to_table, ';');
PREPARE stmt FROM #rename_query;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
END IF;
END LOOP;
CLOSE cur1;
END//
delimiter ;
Usage:
CALL rename_tables('test', 'jos_', '');
Update: This was my first MySQL stored procedure and I ran into the 6 years old bug #5967 which was quite annoying, your variable names must be different from the field names, because if they aren't you'll get NULL values in your variables.
So be aware of that if you decide to write a MySQL stored procedure.