如何在 MySQL 中计算天数?
mysqlmysqli database
首先让我们创建一个表，其中一列存储日期时间，另一列存储天数:
mysql> create table DemoTable ( ShippingDate datetime, CountOfDate int ); Query OK, 0 rows affected (0.52 sec)
下面是使用 insert 命令在表中插入一些记录的查询:
mysql> insert into DemoTable values('2018-01-31',6);
Query OK, 1 row affected (0.11 sec)
mysql> insert into DemoTable values('2016-12-01',15);
Query OK, 1 row affected (0.21 sec)
mysql> insert into DemoTable values('2016-12-01',10);
Query OK, 1 row affected (0.13 sec)
mysql> insert into DemoTable values('2016-12-01',5);
Query OK, 1 row affected (0.17 sec)
mysql> insert into DemoTable values('2019-04-09',3);
Query OK, 1 row affected (1.05 sec)
mysql> insert into DemoTable values('2018-01-31',4);
Query OK, 1 row affected (0.14 sec)
mysql> insert into DemoTable values('2019-04-09',4);
Query OK, 1 row affected (0.14 sec)
以下是使用 select 命令显示表中记录的查询:
mysql> select *from DemoTable;
这将产生以下带有日期和计数的输出:
+---------------------+-------------+ | ShippingDate | CountOfDate | +---------------------+-------------+ | 2018-01-31 00:00:00 | 6 | | 2016-12-01 00:00:00 | 15 | | 2016-12-01 00:00:00 | 10 | | 2016-12-01 00:00:00 | 5 | | 2019-04-09 00:00:00 | 3 | | 2018-01-31 00:00:00 | 4 | | 2019-04-09 00:00:00 | 4 | +---------------------+-------------+ 7 rows in set (0.00 sec)
以下是获取每天总数的查询:
mysql> select date(ShippingDate),sum(CountOfDate) from DemoTable group by date(ShippingDate);
这将产生以下输出:
+--------------------+------------------+ | date(ShippingDate) | sum(CountOfDate) | +--------------------+------------------+ | 2018-01-31 | 10 | | 2016-12-01 | 30 | | 2019-04-09 | 7 | +--------------------+------------------+ 3 rows in set (0.00 sec)
