Tipi data/ora in BigQuery

Introduzione a BigQuery

Matt Forrest

Field CTO

Perché date e ore contano

Filtra facilmente insiemi di dati lunghi
Estrai parti di date/ore
Strategie di partizionamento

Date

Esempio del tipo DATE

SELECT 
    DATE(2010, 05, 19) as launch


/*------------*
 | launch     |
 +------------+
 | 2010-05-19 |
 *------------*/

Timestamp

Esempio di timestamp:

SELECT 
    TIMESTAMP("2010-05-19 00:00:00+00") as launch


/*-------------------------*
 | launch                  |
 +-------------------------+
 | 2010-05-19 00:00:00 UTC |
 *-------------------------*/

Datetime e Time

Esempi di time e datetime:

SELECT
  TIME(12, 00, 00) as noon,

  DATETIME(2019, 05, 19, 00, 00, 00) as launch


/*----------+----------------------*
 | noon     | launch               |
 +----------+----------------------+
 | 12:00:00 | 2019-05-19T00:00:00  |
 *----------+----------------------*/

Parti di date e timestamp

Giorno

DAY, DAYOFWEEK, DAYOFYEAR.

Settimana

WEEK, WEEKDAY, ISOWEEK.

Mese/Anno

MONTH, QUARTER, YEAR, ISOYEAR.

Ora

HOUR, MINUTE, SECOND, MILLISECOND, MICROSECOND.

¹ https://cloud.google.com/bigquery/docs/reference/standard-sql/timestamp_functions#timestamp_trunc

ADD, SUBTRACT e DIFF

Aggiungere cinque giorni

SELECT 
    DATE_ADD(DATE '2010-05-19', 
             INTERVAL 5 DAY) 
             AS five_days_later;


/*--------------------*
 | five_days_later    |
 +--------------------+
 | 2010-05-24         |
 *--------------------*/

Trovare la differenza

SELECT 
    DATE_DIFF(DATE '2010-05-24', 
             DATE '2010-05-19', DAY) 
             AS difference;


/*-------------*
 | difference  |
 +-------------+
 | 5           |
 *-------------*/

EXTRACT

Trovare il giorno della settimana

SELECT 
    EXTRACT(DAYOFWEEK FROM DATE '2010-05-19') 
             AS day_of_week;


/*--------------*
 | day_of_week  |
 +--------------+
 | 4            |
 *--------------*/

FORMAT

SELECT
    FORMAT_DATE(
      '%x', DATE '2010-05-19') 
    AS with_slashes;


/*--------------*
 | with_slashes |
 +--------------+
 | 05/19/10     |
 *--------------*/

SELECT
    FORMAT_DATE(
      '%A', DATE '2010-05-19') 
    AS dow;


/*--------------*
 | dow          |
 +--------------+
 | Wednesday    |
 *--------------*/

¹ https://cloud.google.com/bigquery/docs/reference/standard-sql/format-elements#format_elements_date_time

Data/timestamp correnti

Trovare il timestamp corrente:

SELECT
  CURRENT_TIMESTAMP(); 

/*---------------------------------*
 | current_timestamp               |
 +---------------------------------+
 | 2023-11-13 17:35:25.951432 UTC  |
 *---------------------------------*/

Trovare la data corrente:

SELECT
  CURRENT_DATE();

/*---------------*
 | current_date  |
 +---------------+
 | 2023-11-13    |
 *---------------*/

Cheat sheet

Tipi di dati

Le date sono giorni esatti, i timestamp sono date e ore assolute

Parti di date/timestamp

Parti di una data/timestamp (ad es. MONTH o HOUR)

Add e subtract

Funzioni per sommare o sottrarre parti di data (ad es. DATE_ADD)

Differenza

Differenza tra due date per parte di data (ad es. TIMESTAMP_SUB)

Extract e format

Estrai una parte di una data usando le parti di data, formatta una data (ad es. EXTRACT e FORMAT)

Data/timestamp correnti

Restituisci la data o il timestamp correnti (ad es. CURRENT_TIMESTAMP)

Esercitiamoci!

Introduzione a BigQuery