calculate percentage/repartition of values with a sql query

I have the following table

type	color	value
A	white	true
B	black	false
c	yellow	true
d	red	true
f	green	false

and I want to calculate with a sql query the percentage of rows having value equal to true , here for example we have 3 trues over a total of 5 lines which makes a percentage of 60% of types having a value equal to true , any idea how to fix this please ?

Answer

Do you just want a single value to be returned?

Depending on which RDBMS you’re using boolean values are handled differently, but the basic structure should be similar to…

SELECT
  SUM(CASE WHEN value = true THEN 1 ELSE 0 END) * 1.0 / COUNT(*)
FROM
  yourTable