SQLite query for comparing database value and system time

I want to compare the value which i already stored in database with current system value. and pls give answer for following question

SQLite query for comparing database value and 开发者_JAVA百科system time

That would be an expression, not a query: julianday() < mydate evaluates to true if mydate falls after the current date and time. mydate must be the number of days (with fractional hours) since a particular moment in time in 4714 B.C.

The details are all here, including explanations of how to get dates into and out of different representations, including the Unix epoch.