The power of firstOnly keyword

Sometimes only one record from a table is required, but firstOnly keyword is not used by a developer. For example:

select AccountNum from custTable where custTable.CustGroup == '10'; if (custTable.AccountNum) { ... }

What difference does it make?

Problem description
Compare select statements with and without firstOnly keyword.

Hints
Use SQL Server Profiler for analysis and trace RPC:Starting and RPC:Completed events:

When is it best to use Table::find().Field or select Field from Table?

In this post I am going to analyse the question and define rules for each option.

Problem description
On the one hand, it is a common best practice to select only required information from a database, but quite often an entire record is fetched from the database, even though only one field is actually used. It can be compared to driving a car always on the 1st gear - the engine is fully used, but the car cannot drive fast.
On the other hand, there is a static find method design pattern - the method must be used whenever a record is selected by its key. Find method returns the entire record. Is it contradictory to the common best practice? Let's find out.

How to restrict view datasource fields

A view is specified by a query and there are two ways to define the view query - add existing query or add datasources to Metadata node:

Both options deal with datasources. It is recommended to restrict datasource fields and return only the fields which are actually used. Unused fields generate useless traffic and decrease performance. Is such recommendation relevant for the view Metadata?

Hints
Analyse the view CREATE script in SQL Server Management Studio. You can also jump to the conclusion section.