# count 练习 Joe 建立了一个名为items的表 ``` mysql> select * from items; +----+-----------+ | id | item | +----+-----------+ | 1 | 2 | | 2 | NULL | | 3 | 9 | | 4 | 534214123 | +----+-----------+ ``` 当他执行 ```sql select count(*), count(item) from items; ``` 会得到什么结果?
点击进入[MySQL实战练习环境](https://mydev.csdn.net/product/pod/new?image=cimg-centos7-skilltreemysql&connect=auto&create=auto&utm_source=skill){target="_blank"}。 * `show databases;` 列出所有数据库 * `show tables;` 列出所有表 ## 答案 ``` 3, 4 ``` ## 选项 ### A ``` 4, NULL ``` ### B ``` 3, 3 ``` ### C ``` 1, 0 ``` ### D ``` NULL, NULL ``` ### E ``` 4, 4 ```