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SQL架构：
1 Create table If Not Exists Failed (fail_date date) 2 Create table If Not Exists Succeeded (success_date date) 3 Truncate table Failed 4 insert into Failed (fail_date) values ('2018-12-28') 5 insert into Failed (fail_date) values ('2018-12-29') 6 insert into Failed (fail_date) values ('2019-01-04') 7 insert into Failed (fail_date) values ('2019-01-05') 8 Truncate table Succeeded 9 insert into Succeeded (success_date) values ('2018-12-30') 10 insert into Succeeded (success_date) values ('2018-12-31') 11 insert into Succeeded (success_date) values ('2019-01-01') 12 insert into Succeeded (success_date) values ('2019-01-02') 13 insert into Succeeded (success_date) values ('2019-01-03') 14 insert into Succeeded (success_date) values ('2019-01-06')
Table: Failed
+--------------+---------+
| Column Name | Type |
+--------------+---------+
| fail_date | date |
+--------------+---------+
Primary key for this table is fail_date.
Failed table contains the days of failed tasks.
Table: Succeeded
+--------------+---------+
| Column Name | Type |
+--------------+---------+
| success_date | date |
+--------------+---------+
Primary key for this table is success_date.
Succeeded table contains the days of succeeded tasks.
A system is running one task every day. Every task is independent of the previous tasks. The tasks can fail or succeed.
Write an SQL query to generate a report of period_state for each continuous interval of days in the period from 2019-01-01 to 2019-12-31.
period_state is 'failed' if tasks in this interval failed or 'succeeded' if tasks in this interval succeeded. Interval of days are retrieved as start_date and end_date.
Order result by start_date.
The query result format is in the following example:
Failed table:
+-------------------+
| fail_date |
+-------------------+
| 2018-12-28 |
| 2018-12-29 |
| 2019-01-04 |
| 2019-01-05 |
+-------------------+
Succeeded table:
+-------------------+
| success_date |
+-------------------+
| 2018-12-30 |
| 2018-12-31 |
| 2019-01-01 |
| 2019-01-02 |
| 2019-01-03 |
| 2019-01-06 |
+-------------------+
Result table:
+--------------+--------------+--------------+
| period_state | start date | end date |
+--------------+--------------+--------------+
| present | 2019-01-01 | 2019-01-03 |
| missing | 2019-01-04 | 2019-01-05 |
| present | 2019-01-06 | 2019-01-06 |
+--------------+--------------+--------------+
The report ignored the system state in 2018 as we care about the system in the period 2019-01-01 to 2019-12-31.
From 2019-01-01 to 2019-01-03 all tasks succeeded and the system state was "present".
From 2019-01-04 to 2019-01-05 all tasks failed and system state was "missing".
From 2019-01-06 to 2019-01-06 all tasks succeeded and system state was "present".