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… Read More »