总计的Postgres时间间隔

Question

I have a Postgres table with interval data, such as:

• 0 month
• 1 month
• 1.5 months
• 9 months
• 1 year

I would like to create a view which displays the values, but in total months (so the correct values in my case would be: 0, 1, 1.5, 9, 12). I have tried using:

EXTRACT(MONTHS FROM "MyTable"."Interval"::INTERVAL)

However, this yielded incorrect results (0, 1, 1 , 9, 0 ).

Is there another function, which would display the expected values?

Answer 1

Well, the extract function retrieves subfields such as year or hour from date/time values, not the total time you want,but we can construct the result by ourself, as below:

postgres=# select * from month_table ;
   month    
------------
 0 month
 1 month
 1.5 months
 9 months
 1 year
 2 years
 1.5 years
(7 rows)

postgres=# select                     
    case when month ~ 'month' then regexp_replace(month,' month.*','')::numeric
         when month ~ 'year' then regexp_replace(month,' year.*','')::numeric * 12 end as months
from 
    month_table;
 months 
--------
      0
      1
    1.5
      9
     12
     24
   18.0
(7 rows)