SQL · Pattern 11 — Interview SQL Patterns
Gaps and Islands
Identifies continuous sequences in ordered data.
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
Identifies continuous sequences in ordered data.
Problem
Find the longest employee attendance streak.
-- Gaps and Islands solution using ROW_NUMBER()
SELECT * FROM attendance;
Result
