247AppsStudio Blog

Some point in the future, you’ll have to get rid of some duplicated email records in your database table. How will you do that? Well, here is a handy query for finding duplicates of any field in a table. Suppose you want to find all email addresses in a table that exist more than once, use the query below:

select email_address,
count(email_address) as NumberOccurrences
from table_user_info
group by email_address
having ( count(email_address) > 1 );

This query will give you the results below:

After installing MySQL, go to MySQL directory on your pc, open the file my.ini and change the data directory where you’ll store all your data in the future.  By default, it’ll define your pc’s Documents directory as shown below.

datadir=”C:/Documents and Settings/All Users/Application Data/MySQL/MySQL Server 5.1/Data/”

However you can point it to Data directory under MySQL dir.

When your company decides to reduce the prices of all products to 5% during this difficult economic time, what will you do to adjust the product prices in your database. Here is what I will show you.

If you perform the query directly to production database, first, I would recommend you duplicate the product table in case you enter an incorrect query. I always do this when I run query to change data in database.

Then write you query

UPDATE tbl_products SET price = price – (price * 0.05) ;

If your company just want to reduce the prices of products in a certain category, you can filter by category id.

UPDATE tbl_products SET price = price – (price * 0.05)  where cat_id = 5;