How to create a column in a table and that should throw error when we do SELECT * or SELECT col

Problem: Create a column in a table and that should give an error if we give SELECT * or SELECT of that column Solution: Friends, don’t think toooooo much like how to solve this problem. Here is the simple solution that I got. Just use any computed column and that should not have any syntactical errors but it should have logical error (E..g...

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Greenplum System-Useful Queries

Useful Queries: Query to verify the list of segments in a Greenplum system select * from gp_segment_configuration; Result: Column Value Description Content = -1 Master Node Content...

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Greenplum Best Practises

Best Practices: A distribution key should not have more than 2 columns, recommended is 1 column. While modeling a database, we need to make sure all the tables that gets involved in longer query execution are distributed...

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Greenplum Architecture

Parallel Processing:  Taking all the rows from table and spreading them among many parallel processing units. In greenplum these parallel  processing units are called segments. SMP(symmetric multi processing system):   A...

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How to find and delete the top 100 most used files in Linux/Unix

Steps to find and delete the top 100 most used files in Linux/Unix Command to find most disk space used files: find / -xdev -type f -size +100M -exec du -sh {} ';' | sort -rh | head -n100 Command to delete the content without removing the file > <<filename>> E.g. > sample.txt Here > is used to empty the file Thanks...

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How to Install MySQL on CentOS 7

Steps to Install MySQL on Linux-CentOS 7 Step 1: Download MYSQL repositories wget http://dev.mysql.com/get/mysql57-community-release-el7-9.noarch.rpm Step 2: Prepare repository to install MySQL sudo rpm -Uvh mysql57-community-release-el7-9.noarch.rpm Step...

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