sql server - Clarification in CASE statement in sql -


i came across code assumption made in end of case statement in join , couldn't understand. please tell me purpose of using such method/code.

code:

full outer join #std b on a.empid = b.mgrid                                                    , case                                                           when a.empname not null                                                           a.empname                                                           else a.mgrname                                                        end = b.stdname

the bit don't understand end = b.std. know purpose of it. thanks.

this second predicate of where clause equivalent to:

coalesce(a.empname, a.mgrname) = b.stdname

i.e. a.empname used compare b.stdname, unless a.empname null. in latter case a.mgrname used instead.


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