Why does the EXPLAIN query return NULL everywhere?

Question

MySQL

Actually, the whole question is in the title. Oh yes, even in the column extra returns Impossible. Where to dig???

Answer 1

Impossible WHERE noticed after reading const tables
MySQL has read all const (and system) tables and notice that the WHERE clause is always false.

dba.stackexchange.com/questions/21220/why-am-i-get...
But in general it is necessary to write such questions giving explain of request and structure of tables at least.