What’s the difference between primary key and unique key? Ans:Both Primary & Unique keys are Indexes.

Index:

An index is a structure in a table that orders the data. It allows the database to access data quickly (In MySQL its implemented using B-tree algorithms).

Primary Key:

This is an index that cannot be NULL, Primary Keys are used in building relationships between tables in a database. (an index is automatically created on the primary key). The difference between primary and ordinary keys is that there can be multiple keys, but only one primary key.

Unique Key:
Unique and Index are same, the difference is, in Unique, duplicate are not allowed in any circumstances and that is enforced by database server. Primary key(s) qualify to be Unique on basis
of their uniqueness.

In case, your table has 2 primary keys means that the 2 fields together form one unique key. Each field by itself may have repeating values, but both primary keys combined together must be unique.

The Perl script on the site is working slow. What’s your plan of attack?

Name several reasons why a Web site would not work entirely.

Write an SQL statement that would select only the customers who made multiple orders within a single week.

What version control systems do you use?

How do you configure the maximum number of processes in Apache?

Ans:This arrangement uses more advanced mod_rewrite features to get the translation from virtual host to document root from a separate configuration file. This provides more flexibility but requires more complicated configuration.

The vhost.map file contains something like this:

www.customer-1.com /www/customers/1
www.customer-2.com /www/customers/2
# …
www.customer-N.com /www/customers/N

The http.conf contains this:

RewriteEngine on

RewriteMap lowercase int:tolower

# define the map file
RewriteMap vhost txt:/www/conf/vhost.map

# deal with aliases as above
RewriteCond %{REQUEST_URI} !^/icons/
RewriteCond %{REQUEST_URI} !^/cgi-bin/
RewriteCond ${lowercase:%{SERVER_NAME}} ^(.+)$
# this does the file-based remap
RewriteCond ${vhost:%1} ^(/.*)$
RewriteRule ^/(.*)$ %1/docs/$1

RewriteCond %{REQUEST_URI} ^/cgi-bin/
RewriteCond ${lowercase:%{SERVER_NAME}} ^(.+)$
RewriteCond ${vhost:%1} ^(/.*)$
RewriteRule ^/(.*)$ %1/cgi-bin/$1 [T=application/x-httpd-cgi]

How much memory do you need for Web server app? Describe your logic of calculating this number.

What are response codes 302 and 303?

How do you delete all files with file extension temp recursively on a Linux box?

What Perl tools do you use for coding, testing, debugging?

Do you use DHTML and JavaScript? Describe the projects you’ve used them in.