How to add and drop primary key in SQL Server

If you want to add primary key after you create the table in the sql server, then
1. go to Microsoft SQL Server Management Studio
2. Right click on the database and select new query
3. ALTER TABLE tbl_name ADD PRIMARY KEY(pr_key_column);
tbl_name – name of the table you want to assign primary key
pr_key_column – column/field name which you want it to be primary key

If the pr_key_column is allowed null values, then you can’t assign it as primary key. So if that is the case use this query first:
ALTER TABLE tbl_name ALTER COLUMN pr_key_column datatype not null;

To revoke primary key:
ALTER TABLE tbl_name DROP CONSTRAINT(pr_key_column);

Previous releases of Microsoft Visual Studio 2008 failed error

While you are trying to install MS SQL Server 2008 on the machine which already has Visual studio, you might come up with this problem.

Here is the remedy.
Go to command prompt and move to the MS SQL Server installation DVD like:
C:…>E: – assuming your DVD drive letter is ‘E’
Then provide the following command:
SETUP /action=install /skiprules=vsshellinstalledrule
While you are installing, you might come up with error message but pass it selecting ok.

The other solution might be the trivial one – uninstall VS and install MS SQL Server then install VS – :-(
I hope it will help a lot.

How to change default MySQL directory

Originally it will be located at /var/lib/mysql

Say you want to change it to /home/myApps/mysql

First if the mysql is running stop it: sudo /etc/init.d/mysql stop
and stop the server too: sudo/etc/init.d/apache2 stop

Go to /etc/mysql/my.cnf and edit:
datadir = /var/lib/mysql to datadir = /home/myApps/mysql

Copy files from existing path to the new path
cp -R /var/lib/mysql* /home/myApp/mysql

Grant ownership to new directory for mysql

sudo chown -R mysql:mysql /home/myApp/mysql

then start up your server and mysql – voila.