使用Bigquery，如何使用涉及日期的条件语句

Question

I require a column which counts the number days ie(Order Date - 01Jan2020).

Condition is -> if Order Date lies between 01Jan2020 and 31Mar2020 then (DATE_DIFF('2020-01-31',Order Date, DAY)) else 0
Question -> how to use this condition statement in BigQuery?

Table - Customer ID | Order Date 298 | 2020-02-28 78 | 2020-04-02 31 | 2021-01-09 345 | 2021-09-09 74 | 2020-01-20

I tried -

if((Order Date <'2020-01-01') and (Order Date >'2020-03-31'),(DATE_DIFF('2020-01-31' ,Order Date,  DAY)
,0))

Answer 1

Try below syntax: Once able to run it. Replace current_date with Order_Date. Hope this will work.

select 

if(current_date <'2020-01-01' and current_date >'2020-03-31' ,DATE_DIFF('2020-01-31' ,current_date,  DAY),0);

Answer 2

Try SELECT statement with WHERE clause:

SELECT id, orderdate, DATE_DIFF('2020-01-31', orderdate, DAY) as datediff FROM `yourdataset.ordertable`
WHERE orderdate BETWEEN '2020-01-01' AND '2020-03-31';

Output:

id  orderdate   datediff
298 2020-02-28  -28
74  2020-01-20  11

CASE statement:

SELECT 
  id, 
  orderdate,
  CASE 
      WHEN (orderdate BETWEEN '2020-01-01' AND '2020-03-31') THEN DATE_DIFF('2020-01-31', orderdate, DAY)
      ELSE 0
END AS `datediff`
FROM `yourdataset.ordertable`

Output:

id  orderdate   datediff
78  02/04/20    0
298 28/02/20    -28
345 09/09/21    0
31  09/01/21    0
74  20/01/20    11