Author Archives: Admin

Primarykey in sql

* primarykey uniquely identifies each record in a database table.
* primarykey must contain unique values.
* primarykey column cannot contain null values.
* Each table should have a primarykey and each table have only one primary key.

SQL UNIQUE Constraint

* unique constraint uniquely identifies each record in a database table
*unique and primarykey gives a guarantee for uniqueness for cloumn or set of columns.
*primarykey automatically has a unique constraint on it
*we can have many unique per table
*we can have only one primarykey per table.

Storage Engines in mysql

Mysql support different type of storage engines that will support the table types,myIsam support transaction-safe table and nontransaction-safe tables.

Following are different storage engines

1.MyIsam
2.InnoDb
3.MERGE
4.MEMORY(HEAP)
5.BDB-BerkelyDB
6.EXAMPLE
7.Federated
8.ARCHIVE
9.CSV
10.BLACKHOLE

‘oldsettings’ in aps package

Usually we will use the oldsettings_variablename in the case of updation

for example we need to update the password. In this case we will just compare settings variable value and old settings variable value.if these 2 are not matching then will do the updation

$oldpassword=getenv(‘OLDSETTINGS_password’);// will get the existing password
$newpassword=getenv(‘SETTINGS_password’);// will ge the new password entered.