Correlated Sub-QueriesWhat are they?

select c.*

from customers c, orders o

where c.custid = o.custid

and o.stat = “OPEN”

select c.*

from customers c

where exists (

select “X”

from orders o

where o.custid = c.custid

and o.stat = “OPEN” )

select c.*

from customers c

where custid in (

select custid

from orders o

where o.stat = “OPEN” )

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