第四章 SQL单行函数
1．D
2．D
3．A
4．
--1）
SQL> SELECT cust_id, cname,
NVL(TO_CHAR(birthday, 'yyyy-mm-dd'), 'not avilable'), NVL(TO_CHAR(account), 'no data')
FROM customer;
--2）
SQL> SELECT * FROM customer
WHERE TO_CHAR(birthday, 'yyyy') = '1987';
--3）
SQL> SELECT SUM(account) FROM customer;
5．
SQL> SELECT TO_CHAR(SYSDATE, 'yyyy-mm-dd hh24:mi:ss' )
FROM DUAL;
6．
SQL> SELECT empno, ename, NVL(sal, 0 ) + NVL(comm,0)
FROM emp;
7．
SQL> SELECT ename, sal, job FROM emp
WHERE LENGTH(ename) = 5;
8．
SQL> SELECT ename, hiredate,
ROUND(MONTHS_BETWEEN(SYSDATE, hiredate)) worktime
FROM emp;
9．
SQL> SELECT ename name, LPAD(sal, 15, '$') salary
FROM emp;
10．
SQL> SELECT ename, TO_CHAR(sal, 'L9999.00') FROM emp
WHERE sal > 2000 ORDER BY sal DESC;
11．
SQL> SELECT ename || ' earns ' || sal
||' monthly but wants ' || sal * 3
FROM emp;
12．
SQL> SELECT ename,
TO_CHAR(hiredate, 'yyyy-mm-dd') hiredate,
TO_CHAR(hiredate, 'yyyy"年"mm"月"dd') review
FROM emp;
13．
SQL> SELECT ename, job,
DECODE(job,'PRESIDENT','A',
'MANAGER','B',
'ANALYST','C',
'SALESMAN','D',
'CLERK','E'
) AS "Grade"
FROM EMP;
14．
SQL> SELECT ename, job,
CASE job WHEN 'PRESIDENT' THEN 'A'
WHEN 'MANAGER' THEN 'B'
WHEN 'ANALYST' THEN 'C'
WHEN 'SALESMAN' THEN 'D'
WHEN 'CLERK' THEN 'E'
END AS "Grade"
FROM EMP;
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