Using EXTRACT
You can use EXTRACT() and DATE_PART() to easily create new fields in your queries by extracting sub-fields from a source timestamp field.
Now suppose you want to produce a predictive model that will help forecast DVD rental activity by day of the week. You could use the EXTRACT() function with the dow field identifier in our query to create a new field called dayofweek as a sub-field of the rental_date column from the rental table.
You can COUNT() the number of records in the rental table for a given date range and aggregate by the newly created dayofweek column.
Latihan ini adalah bagian dari kursus
Functions for Manipulating Data in PostgreSQL
Latihan interaktif praktis
Cobalah latihan ini dengan menyelesaikan kode contoh berikut.
SELECT
-- Extract day of week from rental_date
___(___ ___ ___) AS dayofweek
FROM rental
LIMIT 100;