1屉凯、顯示系統(tǒng)時(shí)間(注：日期+時(shí)間)
SELECT NOW();
2动遭、查詢員工號(hào)，姓名神得，工資厘惦，以及工資提高百分之20%后的結(jié)果（NEW salary）
SELECT employee_id,last_name,salary ,salary*1.2 "NEW salary"
FROM employees;
3、將員工的姓名按首字母排序，并寫(xiě)出姓名的長(zhǎng)度（LENGTH）
SELECT LENGTH(last_name) ,SUBSTR(last_name,1,1) 首字符,last_name
FROM employees
ORDER BY 首字符;
4宵蕉、做一個(gè)查詢酝静，產(chǎn)生下面的結(jié)果
# <last_name> earns <salary> monthly but wants <salary*3>
# Dream Salary
# King earns 24000 monthly but wants 72000
SELECT CONCAT(last_name,'earns',TRUNCATE(salary,0),
'monthly but wants',TRUNCATE(salary*3,0)) "DREAM SALARY"
FROM employees
WHERE salary=24000;
5、使用CASE-WHEN羡玛，按照下面的條件
#job grade
#AD_PRES A
#ST_MAN B
#IT_PROG C
#SA_REP D
#ST_CLERK E
#產(chǎn)生下面的結(jié)果
#Last_name Job_id Grade
#king AD_PRES A
SELECT job_id,
CASE job_id
WHEN 'AD_PRES' THEN 'A'
WHEN 'ST_MAN' THEN 'B'
WHEN 'IT_PROG' THEN 'C'
WHEN 'SA_REP' THEN 'D'
END grade
FROM employees;
