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The 90 – 90 rule – SQL Antipattern #009

13 March,2016 by Tom Collins

I read a funny quote the other day from Tom Cargill of Bell labs.

“The first 90 percent of the code accounts for the first 90 percent of the development time. The remaining 10 percent of the code accounts for the other 90 percent of the development time”

Ha Ha! – but in a knowing way.   This rule is not unlike  the Pareto rule relating to the 80/20 principle. Which 20% of effort is giving me 80% of the results? Which 80% of effort is giving me 20% of results?   Read more on DBA and the end of time management


The difference between the two principles is the 90-90 emphasises the almost inevitable truth that when estimating the amount of time to complete programming work , it is difficult to estimate accurately. And even more difficult to identify exactly where the delays will be.

As a DBA involved in Agile projects – 90 – 90 rule seems to apply to most development projects . The Agile principles are elegant , in theory. In practise, if not applied methodically all sorts of delays can occur. The bigger the projects lead to more delays.

Underlying Agile projects there is a reliance on solid architecture and design. If sight is lost – and there is an obsession with continuous delivery of software at the cost of quality , then the 90-90 rule can become more pronounced.

The 90 – 90 rule is part of the SQL Antipattern series. The aim is to identify practises which are

a) a commonly used solution but can lead to bad consequences and

b) There are suitable alternatives, which if used can lead to positive outcomes.


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