ladies and gentlemen, created_time stores string types in my database. How to query the amount of data per hour during the day? how to write this sql?
ladies and gentlemen, created_time stores string types in my database. How to query the amount of data per hour during the day? how to write this sql?
mysql> desc test2;
+----------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
| time_rec | varchar(20) | YES | | NULL | |
+----------+-------------+------+-----+---------+-------+
mysql> select * from test2;
+------+---------------------+
| id | time_rec |
+------+---------------------+
| 1 | 2018-12-12 12:12:12 |
| 2 | 2018-12-12 12:12:14 |
| 3 | 2018-12-12 13:12:12 |
| 4 | 2018-12-13 12:12:12 |
+------+---------------------+
4 rows in set (0.00 sec)
mysql> select count(*),left(time_rec,13) as hour_time from test2 where left(time_rec,10)='2018-12-12' group by hour_time;
+----------+---------------+
| count(*) | hour_time |
+----------+---------------+
| 2 | 2018-12-12 12 |
| 1 | 2018-12-12 13 |
+----------+---------------+
2 rows in set (0.00 sec)you can use segmented queries:
select * from
(select count(*) from you_table where ) as one,
(select count(*) from you_table where ) as two,
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