Problem Description –
Write an SQL query to find the missing customer IDs. The missing IDs are ones that are not in the
Customers table but are in the range between
1 and the maximum
customer_id present in the table.
Notice that the maximum
customer_id will not exceed
Return the result table ordered by
ids in ascending order.
The query result format is in the following example.
Problem Link – Find Missing IDs
Difficulty Level – Medium
-- Step 1: Generate the customer_id sequence between 1 and max using RECURSIVE CTE: WITH RECURSIVE seq AS ( -- initial_query SELECT 1 AS ids UNION ALL -- recursive_query SELECT ids + 1 FROM seq WHERE ids < (SELECT max(customer_id) FROM Customers) ) -- Step 2: Find all the ids in sequence but not in Customers table SELECT ids FROM seq WHERE ids NOT IN (SELECT customer_id FROM Customers) ;