How Can I Avoid Inaccurate Integer Division in PostgreSQL?

Division (/) Inaccuracy in PostgreSQL

When performing division in PostgreSQL, it is important to consider the data types involved to ensure accurate results. In the case described, where the goal is to determine the quantity of software to be sold to recover development costs, integer division can lead to incorrect outcomes.

In the query provided, dev_cost and sell_cost are both integer types. Integer division truncates the result towards zero, meaning that the division of 16000 by 7500 yields 2 instead of the expected 3.

To obtain an accurate result, at least one of the values must be cast to a floating-point type such as float or decimal. Alternatively, the ::decimal syntax can be used to explicitly convert the dev_cost to a decimal implicitly. This coerces the division into a floating-point operation, resulting in a non-truncated division.

Consider the following modified query:

select dev_cost::decimal / sell_cost from software ;

Alternatively, the ceil() function can be used to round the result up to the nearest integer:

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

By utilizing these techniques, accurate division results can be achieved, ensuring that business calculations based on database queries are sound.

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