System time changes can cause major problems to applications and business data. It is extrememly important that any system time changes are planned and explained.
The following command lines can be used to carry out a quick check to see how manu times the system time has been changed.
On a CentOS/RHEL version 6 or equivalent:
grep -c “Time has been changed” /var/log/messages
On a CentOS/RHEL version 7 or equivalent:
journalctl | grep -c "Time has been changed"
The following question was put to me last week:
“In the following table there are month on month totals (perhaps for sales). I would like to show the red, yellow and green trend arrows against each value to show the change against the previous month’s value. Using the same logic I need to show the same coloured arrows for the same data expressed as a percentage change.”
In other words, changing this chart...
Did you know that you can use the SQL Server aggregate functions SUM, COUNT, MAX, MIN and AVG with an OVER Clause now?
Using an OVER clause you can produce individual record values along with aggregate values to different levels, without using a GROUP BY clause. You can also produce running totals, rolling averages, etc.
The examples in this article are based on the AdventureWorks2014 database.
Aggregate To Different Levels with OVER (PARTITION BY ….)
SQL Server 2012 introduced a RESULT SET clause to the EXECUTE statement.
It can be used to specify alternate data types and column names for result sets returned by an EXECUTED statement or Stored Procedure.
The examples in this article are based on the AdvetureWorks2014 database.
The following example shows its use with an ad-hoc query example.
In its out of the box configuration you may find that CentOS Linux has iptables configured to prevent inbound HTTP requests.
You can add access for inbound HTTP requests on port 80 with the following command:
iptables -I INPUT 4 -p tcp -m state --state NEW -m tcp -dport 80 -j ACCEPTLine 4 of the iptables -L output now shows that http is allowed inbound from anywhere:
