Category: MySQL

Solution for MySQL ERROR 1396 (HY000): Operation CREATE USER failed for

Posted on by rchapin

This indicates that the user already exists, or did exist but that all of the data for that user has not been deleted.

As the mysql root user:

REVOKE ALL PRIVILEGES, GRANT OPTION FROM 'user'@'hostname';
DROP USER 'user'@'hostname'

Then re-try creating the user.

Figuring out MySQL ERROR 1005 (HY000) Can’t create table (errno: 150)

Posted on by rchapin

So I’m dumping a database on a remote server to pull down to my local box to do some development.  When loading the mysqldump file I encountered the error:

ERROR 1005 (HY000) at line 8680: Can't create table 'database.table' (errno: 150)

After doing some searching online it seems that is one of the notoriously cryptic MySQL error messages that is woefully overloaded.

I did manage to fix the error (which ended up being a foreign key reference from another table to the one that was erroring out whereby the column definitions were not exactly the same) and learned two important things:

  1. You can invoke the following mysql command immediately after the error to get a more verbose error message (which is what enabled me to solve the problem): SHOW INNODB STATUS
  2. Jason Hinkle has a very nice online reference with a number of possible culprits, and their solutions are listed.

Executing MySQL Queries and Commands from the Command Line to a Remote Server

Posted on by rchapin

Following are a couple of ways to execute SQL on a remote MySQL server via the shell.

Executing SQL directly from the command line:

$ mysql -u uid -p -h remote.host database -e ‘SQL query here;’

Executing SQL from a file on the local host on the remote server:

$ mysql -u uid -p -h remote.host database < file.sql

You can also connect to the remote mysql server and from the command line execute SQL from files on the local drive as such (as long as the file is in the same directory from which the mysql connection is made

mysql> \. file.sql

Notice NO ‘;’ at the end of the command.

Moreover, you can use the following to run commands in your local shell

mysql> \! ls

Will give you the directly listing of the dir from which you invoked the mysql remote connection.

mysql > \! vi file.sql

Will allow you to edit the file on your local drive without having to close the mysql cli.

Executing Dynamically Generated SQL Queries from a Shell Script

Posted on by rchapin

Following is how to generate dynamic SQL in a shell script and then execute those queries.

Let’s say, for instance, that you have a list of tables that you want to flush regularly during development and don’t want to type in the SQL queries each time.  Moreover, you just want to maintain a list of the table names and add and remove from it when necessary and have your script dynamically generate and execute the delete statements.

For the purposes of this tutorial we are running these commands as root to avoid the additional complication of authentication.

The first thing you need is your text file with the list of your tables:

table_list.txt:

table_a
table_b
table_c

delete_data.sh:

table_list.txt:

table_a
table_b
table_c

delete_data.sh:

#!/bin/bash

for i in `cat tables_list.txt`
do

   mysql -u root dbase_name << END_SQL
   delete from ${i};
END_SQL
#
# It is imperitive that the END_SQL redirect identifier
# be on its own line without any leading or trailing spaces
#

done

The script will run, will make a connection to MySQL and then execute the command with the dynamically generated target table.

This will work with other databases other than MySQL as well.

© 2005 Ryan Chapin