Division ( / ) not giving my answer in postgresql

问题

I have a table software and columns in it as dev_cost, sell_cost. If dev_cost is 16000 and sell_cost is 7500.

How do I find the quantity of software to be sold in order to recover the dev_cost?

I have queried as below:

select dev_cost / sell_cost from software ;

It is returning 2 as the answer. But we need to get 3, right?

What would be the query for that? Thanks in advance.

回答1:

Your columns have integer types, and integer division truncates the result towards zero. To get an accurate result, you'll need to cast at least one of the values to float or decimal:

select cast(dev_cost as decimal) / sell_cost from software ;

or just:

select dev_cost::decimal / sell_cost from software ;

You can then round the result up to the nearest integer using the ceil() function:

select ceil(dev_cost::decimal / sell_cost) from software ;

(See demo on SQLFiddle.)

回答2:

You can cast integer type to numeric and use ceil() function to get the desired output

The PostgreSQL ceil function returns the smallest integer value that is greater than or equal to a number.

SELECT 16000::NUMERIC / 7500 col 
      ,ceil(16000::NUMERIC / 7500) 

Result:

col                  ceil 
------------------   ---- 
2.1333333333333333     3    

So your query should be

select ceil(dev_cost::numeric/sell_cost) 
from software

回答3:

You can also cast your variable to the desired type, then apply division:

 SELECT (dev_cost::numeric/sell_cost::numeric);

You can round your value , and specify the number of digits after point:

SELECT TRUNC((dev_cost::numeric/sell_cost::numeric),2);

回答4:

This query will round result to next integer

select round(dev_cost ::decimal / sell_cost + 0.5)

来源：https://stackoverflow.com/questions/34504497/division-not-giving-my-answer-in-postgresql