Union VS Union all in terms of performance

Many times  unskilled or novice computer programmers when are under pressure and the time is running fast towards the end, usually  they copy the code from a place and paste it into another place, without the full understanding of the implications.

Let's take a look at the differences between UNION and UNION ALL operators.

Pivot my table

Let's take a look to a simple example of how create a pivot table, useful when you work with reports and summary statistics.

The table employee contains 10 records with the employees details (Name, salary, role and year of reference)

How get single items from a list of values

Sometimes when we develop procedures or functions we have to handle list of values, passed as parameters (for example).
Let's see a simple script helping us to split in single values the list of values, using the powerful WITH clause.

Do you need to import a file into a table? do it simple with External Table.

Very often we work with environments that cannot be linked directly (with a DB link for example) and we have to acquire data by text files.
In order to reach that goal I have seen developers write procedures with many lines of code, variables end complicating their lives with loops.
Just do it simple, with "ET".