MySQL Bugs: #75936: Ability to round to a number of significant figures

Bug #75936	Ability to round to a number of significant figures
Submitted:	17 Feb 2015 17:14
Reporter:	Michael Grazebrook	Email Updates:
Status:	Open	Impact on me:	None
Category:	MySQL Server: DML	Severity:	S4 (Feature request)
Version:	6.1.6	OS:	Any
Assigned to:		CPU Architecture:	Any

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Description:
It's generally a good idea to round data to an appropriate number of significant figures to avoid misrepresenting its accuracy.

For example 0.0012345 rounded to 2 significant figures is 0.0012, 12345.67 would be 12000

How to repeat:
This expression has the desired functionality:

ROUND(@x,2-floor(LOG10(abs(@x))))

but it's ugly and hard for people who don't understand logarithms.

Suggested fix:
Provide a function to round a value to a number of significant figures.