Posts

Generate Date from a range in Mysql and pad the results where no date is present

If you want to generate dates, MYSQL doesn’t have a range function, so I wrote a work around for the same. So how  it works is I have reused a code to generate numbers from my previous post. So I added date function to that query and reduce the generated  …

Generate 1 to 1000 in mysql

Sometimes its necessary to have thousand rows to join or generate new values, we need to get the thousand rows first. For this I used union of numbers 0-9.  I have joined four of these to get to four digit values. So here is the code:



SELECT @row := …

Display row number in Mysql Select Query

How many times did want to have the row number or the position of the row in the selected query? I had many cases where I needed this feature. I needed the feature for printing the rank of a person where each row is the mark of the person. So lets see how  …

Create a table like another table or from a select query

There are some cases where we need to create a table similar or exactly same as another table. The easiest and best way is use create table along with additional parameters. We can create a table similar to another table without data and with data. Creat …

Get the nth Word from a text field in mysql

I had a requirement to get the nth word out of a string and sort or order by the same. This is used when the text is stored in a purticular format and you would want to order it according to that or group it or so on. So how is it done? We do it using a  …

Important MySQL DBA Interview Questions

Here are a few sets of interview questions expected for MySQL DBA position.These are compilation of the usual questions from various DBA texts: What is Log Switch? – The point at which ORACLE ends writing to one online redo log file and begins writing to …

Simplest way to remove trailing zeros of decimal numbers

This is a simple method I found to remove or strip trailing zeros of a decimal number. The function accepts the decimal number and return the trimmed value back. It removes all the redundant zeros in the number after the decimal point and if no number othe …

Batch Insert/Update for Mysql in Java

Large inserts/Updates are a costly operation. One foolish way that I used to do is to run each update or insert query one at a time. Its incredibly slow. With most of the systems currently the latency is what is killing the performance not the CPU. Hence l …

Group by Date when Stored in Mysql DataBase as Date Time

I have a table called date_count with 2 columns one is a value and another is a date time, say called date_time in mysql. Date Time in mysql is stored as dd-mm-yy hh:mm:ss. The issue comes when I need to get the number of rows per day. As its stored as dat …

Ontology Linked Data

The following is a Assignment on Ontology and Linked Data and the evolution of data which lead to the use of ontology in web. Thanks to my teammates Bharath Gowda and Sravani Thota for working on the same. Ontology And Linked Data An ontology formally r …