Collect Statistics and EXPLAIN

[scarletAni]

On giving the EXPLAIN statement affter collecting statistics also , I get to see "no confidence" rows. How does Collect Statistics help ? And how does and EXPLAIN statement help to identify whether a collect statistics was done or not ?

 

[dnoeth]

There may be "No confidence" even with statistics, if the statistics can't be used to calculate the expected number of rows, typically because of some calculation/functions on that column, e.g. col like '%tttt%'

So maybe just post query/explain.

Dieter