Category: DBMS

Database Management Systems

How the IF Statement Works in SQL Server

Posted on by Ian

Most (probably all) programming languages include some form of the IF statement that allows programmers to write conditional code. That is, code that will execute only if a certain condition is true.

It’s a very simple concept. Basically it goes like this:

“If this, do that.”

Most languages simply call it IF, but some have their own twist on the name (for example, in ColdFusion/CFML, it’s called CFIF).

In any case, they essentially do the same thing.

In SQL Server (or more precisely, its programming language T-SQL) it’s called IF.

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Calculate the Age in Years in PostgreSQL

Posted on by Ian

Postgres has the age() function that returns the age in years, months, and days based on two dates.

This works fine unless you only want to return the age in years.

For example, you simply want to return a person’s age based on their birthday. You want something like 32 instead of 32 years 4 mons 67 days, which is what age() is likely to return.

Fortunately there’s an easy way to do this in PostgreSQL.

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Convert a Julian Day to a Date in PostgreSQL

Posted on by Ian

Here are two ways to convert a given Julian day to its date value in PostgreSQL.

The first method directly inputs the Julian day into the date data type.

The second method uses the to_date() function to return the same result.

Julian day is the number of days since Monday, January 1, 4713 BC using the proleptic Julian calendar, which is November 24, 4714 BC, in the proleptic Gregorian calendar.

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