Remove First Part of a Column Value

Let's say you have some values in your MySQL database that look like this:​

a_180.0/v1355635866/r0y0ajbjiqry42tqscof.jpg

You want to to remove the first bit in a bulk process (the a_180.0/) and you don't want to have to write a 10 line Python script.  Well then, do it in good 'ol SQL.​

Table: event_photo, Column: original_image_id

 UPDATE event_photo SET original_image_id = TRIM(LEADING 'a_180.0/' FROM original_image_id);​

If you want to remove the .jpg part of the column value you can do this:

UPDATE event_photo SET original_image_id = TRIM(TRAILING '.jpg' FROM original_image_id);​

If you have spaces in the front or back of the value and you want to remove those just do this:​

UPDATE event_photo SET original_image_id = TRIM(original_image_id);

Set MySQL root password to NULL

​Not recommended but if needed...

From the command line

sudo service mysql stop
sudo mysqld_safe --skip-grant-tables --skip-networking &
mysql -uroot

From MySQL

use mysql;
update user set password=null where User='root';
flush privileges;
quit;

Drop a Foreign Key in MySQL

​Fiddling with the removal of a foreign key in MySQL can drive an engineer mad.  In order to remove the key you must use the name of the constraint in the drop statement - not the name of the index.

The show command lists out the DDL for the table, including the created foreign keys:​

mysql> show create table t1;

...
  CONSTRAINT `MY_TABLE_FK05` FOREIGN KEY (`FLIGHT_ID`,
`USER_ID`) REFERENCES `MY_OTHER_TABLE` (`FLIGHT_ID`,
`USER_ID`)

You can then issue the drop command with the name of the constraint (yeah, not really intuitive)

mysql> alter table t1 drop foreign key MY_TABLE_FK05;
Query OK, 0 rows affected (0.03 sec)
Records: 0  Duplicates: 0  Warnings: 0