SELCET数据查询例题2——单行函数

答案代码如下：

#1、
SELECT NOW();

#2、
SELECT employee_id,last_name,salary,salary*1.2 AS "new salary"
FROM employees;

#3、
SELECT LENGTH(last_name) AS 长度,SUBSTR(last_name,1,1) AS 首字符,last_name
FROM employees
ORDER BY 首字符;

#4、
SELECT CONCAT(last_name,' earns ',salary,' monthly but wants ',salary*3) AS "Dream Salary"
FROM employees
WHERE salary=24000;

#5、
SELECT last_name,job_id AS job,
CASE job_id
WHEN 'AD_PRES' THEN 'A'
WHEN 'ST_MAN' THEN 'B'
WHEN 'IT_PROG' THEN 'C'
WHEN 'SA_PRE' THEN 'D'
WHEN 'ST_CLERK' THEN 'E'
END AS Grade
FROM employees
WHERE job_id = 'AD_PRES';

这是我网课学习到的几个题目，在这里记录总结。