我在数据库menagerie
中有以下表格pet
:
+--------+-------------+---------+------+------------+------------+
| name | owner | species | sex | birth | death |
+--------+-------------+---------+------+------------+------------+
| Tommy | Salman Khan | Lebre | NULL | 1999-01-13 | 0000-00-00 |
| Bowser | Diane | dog | m | 1981-08-31 | 1995-07-29 |
+--------+-------------+---------+------+------------+------------+
现在,如果我运行以下查询:
select owner, curdate() from pet;
我得到以下输出:
+-------------+------------+
| owner | curdate() |
+-------------+------------+
| Salman Khan | 2016-09-12 |
| Diane | 2016-09-12 |
+-------------+------------+
输出显示owner
的所有值,以及每行curdate()
返回的值.
现在,如果我运行以下查询:
select owner, count(*) from pet;
我得到以下输出:
+-------------+----------+
| owner | count(*) |
+-------------+----------+
| Salman Khan | 2 |
+-------------+----------+
我的问题是,在第一个示例中,curdate()
和count()
函数之间的区别是什么,这使得MySQL
输出第二个owner
Diane?