how to extract date from JSON data type column in Postgres

Question

I have a column open_houses that's JSON data type and it looks like this:

open_houses
[{"Date": "2017-08-13", "ToTime": "4:00PM", "FromTime": "2:00PM"}]
[{"Date": "2017-08-12", "ToTime": "3:00PM", "FromTime": "1:00PM"}]
[{"Date": "2017-08-12", "ToTime": "4:00PM", "FromTime": "2:00PM"}]
[{"Date": "2017-08-13", "ToTime": "3:00PM", "FromTime": "1:00PM"}]

When I try to extract 'Date' from this column I get an error -

SELECT ...
FROM   prod.vw_listing
WHERE  ...
       ...
       AND open_houses[1] -> 'Date'::DATE >= current_date;

Error:

cannot subscript type jsonb because it is not an array

Answer 1

使用->操作数获取 json 数组元素：

with vw_listing (open_houses) as ( values 
    ('[{"Date": "2017-08-13", "ToTime": "4:00PM", "FromTime": "2:00PM"}]'::jsonb),
    ('[{"Date": "2017-08-12", "ToTime": "3:00PM", "FromTime": "1:00PM"}]'),
    ('[{"Date": "2017-08-12", "ToTime": "4:00PM", "FromTime": "2:00PM"}]'),
    ('[{"Date": "2017-08-13", "ToTime": "3:00PM", "FromTime": "1:00PM"}]')
)
select (open_houses -> 0 ->> 'Date')::date
from vw_listing
;
    date    
------------
 2017-08-13
 2017-08-12
 2017-08-12
 2017-08-13

Answer 2

我能够通过这样做来解决这个问题：

SELECT ...

FROM   prod.vw_listing
WHERE  ...
       AND (open_houses -> 0 ->> 'Date')::date>= current_date;