Relation Constructors

There are multiple options to create temporary relations as part of query definitions. These relations exist only for the execution of the query that defines them.

Using VALUES

VALUES allows you to create a multi-column temporary relation where the values in the relation are explicitly defined in the statement.

A simple example is as follows:

SELECT * 
  FROM (
         VALUES ('High', 3),
                ('Medium', 2),
                ('Low', 1)
       ) AS ratings (name, rating);

Result:

 name   | rating
--------+--------
 High   |      3
 Medium |      2
 Low    |      1

Using UNNEST

UNNEST allows you to create a single column temporary relation where the values in the relation are explicitly defined in the statement.

A simple example is as follows:

SELECT *
  FROM UNNEST((1,2,3)) AS TEMP;

Result:

 unnest 
--------
      1
      2
      3

Note

The values in the UNNEST function are in two sets of parenthesis. The function accepts a list of values, parenthesis is used to wrap parameters to functions and also used to define lists.

Using generate_series

generate_series allows you to create series by defining the bounds of the series, and optionally, an interval to step between values in the created series.

generate_series supports the following variations:

Form	Types	Description
generate_series(start, stop)	NUMERIC, NUMERIC	Generate a NUMERIC series between 'start' and 'stop', with a step of 1
generate_series(start, stop, step)	NUMERIC, NUMERIC, NUMERIC	Generate a NUMERIC series between 'start' and 'stop', with an explicit step size
generate_series(start, stop, interval)	TIMESTAMP, TIMESTAMP, INTERVAL	Generate a TIMESTAMP series between 'start' and 'stop', with a given interval

Two parameter Example:

SELECT *
  FROM generate_series(2, 4) AS series;

 series 
--------
      2
      3
      4

Three parameter NUMERIC Example:

SELECT *
  FROM generate_series(-5, 5, 5) AS series;

 series 
--------
     -5
      0
      5

Three parameter TIMESTAMP example:

SELECT *
  FROM generate_series('2020-01-01', '2025-12-31', '1y') AS series;

           series 
------------------
 2020-01-01 00:00
 2021-01-01 00:00
 2022-01-01 00:00
 2023-01-01 00:00
 2024-01-01 00:00
 2025-01-01 00:00

Interval Definitions

Intervals are defined quantifying one or more periods which make up the interval, supported periods and their notation are:

Recognized interval parts for the GENERATE_SERIES function are:

Period	Symbol	Aliases
Years	year / years	y / yr / yrs
Months	month / months	mo / mon / mons / mth / mths
Weeks	week / weeks	w / wk / wks
Days	day / days	d
Hours	hour / hours	h / hr / hrs
Minutes	minute / minutes	m / min / mins
Seconds	second / seconds	s / sec / secs

Where required, periods can be combined to define more complex intervals, for example 1h30m represents one hour and 30 minutes.

Using FAKE

FAKE creates a table of random integers from provided row and column counts. This functionality has limited application outside of creating datasets for testing.

A simple example is as follows:

SELECT * 
  FROM FAKE(3, 2) AS temp; 

Example Result:

   column_0 │   column_1 
------------┼------------
      32981 │      50883
       5037 │      42087
      51741 │      49456

FAKE supports optionally providing types and names for the columns, these optional features can be used together.

SELECT *
  FROM FAKE(3, (NAME, INTEGER, VARCHAR)) AS temp(user, age, password)

Example Result:

 user            │       age  │ password
-----------------┼------------┼-----------------
 Stephanie Wiley │  195792458 │ 94275740545bfd0 
 Charlie Curry   │ 1970388722 │ af94b1eda94155e8
 Wayne Lyons     │ 4205624016 │ ae883b48b8cd0   

The following column types are able to be faked:
- INTEGER
- VARCHAR (between 8 and 24 randomly selected alpha numeric characters)
- BOOLEAN
- DECIMAL
- DOUBLE (random floating point number between 0 and 1)
- TIMESTAMP (randomly selected date between 1960-01-01 and 2100-12-31)
- AGE (an INTEGER value between 0 and 100)
- NAME (a randomly generated english name as a VARCHAR)