SQL · Pattern 11 — Interview SQL Patterns
Duplicate Records
Groups rows to identify duplicate values.
Source data — Pattern 11: Interview SQL Patterns
All queries run against the shared employees table (see schema.sql). Topics 71 and 72 introduce an orders table to solve consecutive records and gaps-and-islands problems. Topics 73 and 74 introduce a monthly_sales table to demonstrate PIVOT and UNPIVOT operations.
What it does
Groups rows to identify duplicate values.
Problem
Find duplicate email addresses.
SELECT email,COUNT(*)
FROM employees
GROUP BY email
HAVING COUNT(*)>1;
Result
