Finding Duplicate Fields in a Database Table

Occasionally it is necessary to find duplicate fields within a database table.  The following query can be used to accomplish this easily.
SELECT *
FROM 'table'
WHERE ('item' IN (SELECT 'item'
FROM 'table'
GROUP BY 'item'
HAVING COUNT(*) > 1))
ORDER BY 'item'

This will list all rows in the desired ‘table’ where the given field (‘item’) is duplicated. This is a great query to use if you want to find duplicate email addresses in a database, or any other field that may be duplicated.

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Problem Installing Typo Gem

We have a rails server that we wanted to install the typo gem onto.  Alas, our attempts to install the gem kept failing with the following error:

Building native extensions.  This could take a while...
ERROR:  Error installing typo:
	ERROR: Failed to build gem native extension.

/usr/bin/ruby1.8 extconf.rb install typo
checking for fdatasync() in -lrt... yes
checking for sqlite3.h... no

make
make: *** No rule to make target `ruby.h', needed by `sqlite3_api_wrap.o'.  Stop.
 

If you are seeing this error, it means you are likely missing a SQLite3 library or 2. We always use MYSQL, so we did not have any SQLite3 packages installed. Since it was failing on a build, we installed the libsqlite3-dev package. This was all we needed to do and the typo gem installed perfectly with all its dependencies.

On Ubuntu, do the following to install:

sudo apt-get install libsqlite3-dev

Redhat\Centos will be different (for us, substitute apt-get for yum)
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