SQL Select Count in Where Clause Performance issue -

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i have following sql query performs horribly due select count(1) statement in clause. can suggest way speed up? idea want rows returned there 1 invoice found.

select people.name, people.address  people  ((select count(1) invoices invoices.pid = people.id)=1)

so, try join this

select people.name, people.address     people     join    invoices on invoices.pid = people.id group    people.name, people.address  having    count(*) = 1

i'd hope have indexes, @ least on invoices.pid , people.pid, name, address


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