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Creating a Date Dimension Table in PostgreSQL

If you’ve ever read any of Ralph Kimball’s data warehouse books or have any experience with modeling data in the Kimball style, you know that a date dimension is a key part of any star schema.

You probably found resources for creating Oracle, SQL Server or MySQL but may have had difficulty finding SQL to create a date dimension table for PostgreSQL.

Here’s a bit of code adapted from the PostgreSQL wiki that I like for creating the ever necessary date dimension in PostgreSQL.

DROP TABLE if exists d_date;
CREATE TABLE d_date
(
date_dim_id INT NOT NULL,
date_actual DATE NOT NULL,
epoch BIGINT NOT NULL,
day_suffix VARCHAR(4) NOT NULL,
day_name VARCHAR(9) NOT NULL,
day_of_week INT NOT NULL,
day_of_month INT NOT NULL,
day_of_quarter INT NOT NULL,
day_of_year INT NOT NULL,
week_of_month INT NOT NULL,
week_of_year INT NOT NULL,
week_of_year_iso CHAR(10) NOT NULL,
month_actual INT NOT NULL,
month_name VARCHAR(9) NOT NULL,
month_name_abbreviated CHAR(3) NOT NULL,
quarter_actual INT NOT NULL,
quarter_name VARCHAR(9) NOT NULL,
year_actual INT NOT NULL,
first_day_of_week DATE NOT NULL,
last_day_of_week DATE NOT NULL,
first_day_of_month DATE NOT NULL,
last_day_of_month DATE NOT NULL,
first_day_of_quarter DATE NOT NULL,
last_day_of_quarter DATE NOT NULL,
first_day_of_year DATE NOT NULL,
last_day_of_year DATE NOT NULL,
mmyyyy CHAR(6) NOT NULL,
mmddyyyy CHAR(10) NOT NULL,
weekend_indr BOOLEAN NOT NULL
);
ALTER TABLE public.d_date ADD CONSTRAINT d_date_date_dim_id_pk PRIMARY KEY (date_dim_id);
CREATE INDEX d_date_date_actual_idx
ON d_date(date_actual);
COMMIT;
INSERT INTO d_date
SELECT TO_CHAR(datum,'yyyymmdd')::INT AS date_dim_id,
datum AS date_actual,
EXTRACT(epoch FROM datum) AS epoch,
TO_CHAR(datum,'fmDDth') AS day_suffix,
TO_CHAR(datum,'Day') AS day_name,
EXTRACT(isodow FROM datum) AS day_of_week,
EXTRACT(DAY FROM datum) AS day_of_month,
datum - DATE_TRUNC('quarter',datum)::DATE +1 AS day_of_quarter,
EXTRACT(doy FROM datum) AS day_of_year,
TO_CHAR(datum,'W')::INT AS week_of_month,
EXTRACT(week FROM datum) AS week_of_year,
TO_CHAR(datum,'YYYY"-W"IW-') || EXTRACT(isodow FROM datum) AS week_of_year_iso,
EXTRACT(MONTH FROM datum) AS month_actual,
TO_CHAR(datum,'Month') AS month_name,
TO_CHAR(datum,'Mon') AS month_name_abbreviated,
EXTRACT(quarter FROM datum) AS quarter_actual,
CASE
WHEN EXTRACT(quarter FROM datum) = 1 THEN 'First'
WHEN EXTRACT(quarter FROM datum) = 2 THEN 'Second'
WHEN EXTRACT(quarter FROM datum) = 3 THEN 'Third'
WHEN EXTRACT(quarter FROM datum) = 4 THEN 'Fourth'
END AS quarter_name,
EXTRACT(isoyear FROM datum) AS year_actual,
datum +(1 -EXTRACT(isodow FROM datum))::INT AS first_day_of_week,
datum +(7 -EXTRACT(isodow FROM datum))::INT AS last_day_of_week,
datum +(1 -EXTRACT(DAY FROM datum))::INT AS first_day_of_month,
(DATE_TRUNC('MONTH',datum) +INTERVAL '1 MONTH - 1 day')::DATE AS last_day_of_month,
DATE_TRUNC('quarter',datum)::DATE AS first_day_of_quarter,
(DATE_TRUNC('quarter',datum) +INTERVAL '3 MONTH - 1 day')::DATE AS last_day_of_quarter,
TO_DATE(EXTRACT(isoyear FROM datum) || '-01-01','YYYY-MM-DD') AS first_day_of_year,
TO_DATE(EXTRACT(isoyear FROM datum) || '-12-31','YYYY-MM-DD') AS last_day_of_year,
TO_CHAR(datum,'mmyyyy') AS mmyyyy,
TO_CHAR(datum,'mmddyyyy') AS mmddyyyy,
CASE
WHEN EXTRACT(isodow FROM datum) IN (6,7) THEN TRUE
ELSE FALSE
END AS weekend_indr
FROM (SELECT '1970-01-01'::DATE+ SEQUENCE.DAY AS datum
FROM GENERATE_SERIES (0,29219) AS SEQUENCE (DAY)
GROUP BY SEQUENCE.DAY) DQ
ORDER BY 1;
COMMIT;