怎样建设文章网站/高端seo服务
当前选择的数据库
命令：mysql> select database();
MySQL中SELECT命令类似于其他编程语言里的print或者write，你可以用它来显示一个字符串、数字、数学表达式的结果等等。如何使用MySQL中SELECT命令的特殊功能？
1.显示MYSQL的版本
mysql> select version();
±----------------------+
| version() |
±----------------------+
| 6.0.4-alpha-community |
±----------------------+
1 row in set (0.02 sec)
显示当前时间
mysql> select now();
±--------------------+
| now() |
±--------------------+
| 2009-09-15 22:35:32 |
±--------------------+
1 row in set (0.04 sec)
显示年月日
SELECT DAYOFMONTH(CURRENT_DATE);
±-------------------------+
| DAYOFMONTH(CURRENT_DATE) |
±-------------------------+
| 15 |
±-------------------------+
1 row in set (0.01 sec)
SELECT MONTH(CURRENT_DATE);
±--------------------+
| MONTH(CURRENT_DATE) |
±--------------------+
| 9 |
±--------------------+
1 row in set (0.00 sec)
SELECT YEAR(CURRENT_DATE);
±-------------------+
| YEAR(CURRENT_DATE) |
±-------------------+
| 2009 |
±-------------------+
1 row in set (0.00 sec)
显示字符串
mysql> SELECT “welecome to my blog!”;
±---------------------+
| welecome to my blog! |
±---------------------+
| welecome to my blog! |
±---------------------+
1 row in set (0.00 sec)
当计算器用
select ((4 * 4) / 10 ) + 25;
±---------------------+
| ((4 * 4) / 10 ) + 25 |
±---------------------+
| 26.60 |
±---------------------+
1 row in set (0.00 sec)
串接字符串
select CONCAT(f_name, " ", l_name)
AS Name
from employee_data
where title = ‘Marketing Executive’;
±--------------+
| Name |
±--------------+
| Monica Sehgal |
| Hal Simlai |
| Joseph Irvine |
±--------------+
3 rows in set (0.00 sec)
注意：这里用到CONCAT()函数，用来把字符串串接起来。另外，我们还用到以前学到的AS给结果列’CONCAT(f_name, " ", l_name)'起了个假名。