Create report-contiguous-dates.sql

Author: kamyu104

MySQL/report-contiguous-dates.sql

@@ -0,0 +1,27 @@
+# Time:  O(nlogn)
+# Space: O(n)
+
+SELECT state     AS period_state, 
+       Min(date) AS start_date, 
+       Max(date) AS end_date 
+FROM   (SELECT state, 
+               date, 
+               @rank := CASE 
+                          WHEN @prev = state THEN @rank 
+                          ELSE @rank + 1 
+                        end   AS rank, 
+               @prev := state AS prev 
+        FROM   (SELECT * 
+                FROM   (SELECT fail_date AS date, 
+                               "failed"  AS state 
+                        FROM   failed 
+                        UNION ALL 
+                        SELECT success_date AS date, 
+                               "succeeded"  AS state 
+                        FROM   succeeded) a 
+                WHERE  date BETWEEN '2019-01-01' AND '2019-12-31' 
+                ORDER  BY date ASC) b, 
+               (SELECT @rank := 0, 
+                       @prev := "unknown") c) d 
+GROUP  BY d.rank 
+ORDER  BY start_date ASC