Postgres query to check a string is a number

Question

Can anyone tell me the query to check whether a string is a number(double precision). It should return true if the string is number. else it should return false.

con

Answer 1

If you want to check with exponential , +/- . then the best expression is :

^[-+]?[0-9]*\.?[0-9]+([eE][-+]?[0-9]+)?$

resulting in:

select '12.41212e-5' ~ '^[-+]?[0-9]*\.?[0-9]+([eE][-+]?[0-9]+)?$' ;

as true.

The expression is from: https://www.regular-expressions.info/floatingpoint.html

You can check for other types of numbers, for example if you expect decimal, with a sign.

 select '-12.1254' ~ '^[-+]?[0-9]*\.?[0-9]+$';