SQL for No Transaction

Question

Dear All,
I have two tables 1. Cities 2. Transactions. There are 100 cities and each city is having minimum 100 transactions per day. Transaction table contains city name which is same in Cities table. I want to write a query which should tell me which city has made NO TRANSACTION on any particular day. How application works if there is any transaction it inserts row for each transaction in Transactions table if no transaction no entry in Transaction table. I am looking for those cities who are not having any activity or transaction in a said day.
Can any one help on this and I will really appreciate any one's help in this regards.
Thnaks

Answer 1

It's always nice to have the DDL for the tables in question and some sample data.
I've assumed the date column in the transaction table has a time element to it.
I've also assumed that the input parameter is a string datatype. If it was of datatype DATE then TO_DATE should be omitted.
A NOT EXISTS predicate is the most natural way to express this logic.
SELECT *
FROM   cities c
WHERE  NOT EXISTS (SELECT 1
                   FROM   transactions t
                   WHERE  t.city_name         = c.city_name
                   AND    t.transaction_date >= TO_DATE(:date_in_question,'DD-MON-YYYY')
                   AND    t.transaction_date <  TO_DATE(:date_in_question,'DD-MON-YYYY') + 1);