When working with the interval data type in PostgreSQL, you can change the way the interval output is formatted.
You have a choice of four formats that your intervals can be output in.
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Calculate the Age in Years in PostgreSQL
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.
Continue readingGet the Week Number from a Date in PostgreSQL
In PostgreSQL you can use the extract() function to get the week number from a date.
You can also use the date_part() function to do the same thing.
Get the Short Day Name in PostgreSQL
In PostgreSQL, you can use the to_char() function to get the short day name from a date.
By “short day name” I mean the abbreviated day name, for example Fri, Mon, etc.
The to_char() function accepts two parameters; the date and the format string with which to format that date.
Get the Day from a Date in PostgreSQL
In PostgreSQL you can use the extract() function to get the day from a date.
You can also use date_part() to do the same thing.
When extracting the day from a date, you need to specify what sense of the word “day” you mean. For example, “day of week”, “day of month”, “day of year”, etc.
Convert a Julian Day to a Date in PostgreSQL
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.
Continue readingHow AT TIME ZONE Works in PostgreSQL
In PostgreSQL, you can use the AT TIME ZONE clause to convert a timestamp to another timezone.
How make_interval() Works in PostgreSQL
In PostgreSQL, the make_interval() function creates an interval from years, months, weeks, days, hours, minutes and seconds fields.
You provide the years, months, weeks, days, hours, minutes and/or seconds fields, and it will return an interval in the interval data type.
Continue readingHow make_timestamptz() Works in PostgreSQL
In PostgreSQL, the make_timestamptz() function allows you to create a timestamp with time zone from its year, month, day, hour, minute and seconds fields, as well as an optional timezone field.
How make_date() Works in PostgreSQL
In PostgreSQL, the make_date() function allows you to create a date from its separate year, month and day fields.
Each date part is provided as an integer, and the result is returned as a date.
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