37.LAST_DAY
返回日期的最后一天
SQL> select to_char(sysdate,'yyyy.mm.dd'),to_char((sysdate)+1,'yyyy.mm.dd') from dual;
TO_CHAR(SY TO_CHAR((S
---------- ----------
2004.05.09 2004.05.10
SQL> select last_day(sysdate) from dual;
LAST_DAY(S
----------
31-5月 -04
38.MONTHS_BETWEEN(date2,date1)
給出date2-date1的月份
SQL> select months_between('19-12月-1999','19-3月-1999') mon_between from dual;
MON_BETWEEN
-----------
9
SQL>selectmonths_between(to_date('2000.05.20','yyyy.mm.dd'),to_date('2005.05.20','yyyy.mm.dd')) mon_betw from dual;
MON_BETW
---------
-60
39.NEW_TIME(date,'this','that')
給出在this時區=other時區的日期和時間
SQL> select to_char(sysdate,'yyyy.mm.dd hh24:mi:ss') bj_time,to_char(new_time
2 (sysdate,'PDT','GMT'),'yyyy.mm.dd hh24:mi:ss') los_angles from dual;
BJ_TIME LOS_ANGLES
------------------- -------------------
2004.05.09 11:05:32 2004.05.09 18:05:32
40.NEXT_DAY(date,'day')
給出日期date和星期x之后計算下一個星期的日期
SQL> select next_day('18-5月-2001','星期五') next_day from dual;
NEXT_DAY
----------
25-5月 -01
41.SYSDATE
用來得到系統的當前日期
SQL> select to_char(sysdate,'dd-mm-yyyy day') from dual;
TO_CHAR(SYSDATE,'
-----------------
09-05-2004 星期日
trunc(date,fmt)按照給出的要求將日期截斷,如果fmt='mi'表示保留分,截斷秒
SQL> select to_char(trunc(sysdate,'hh'),'yyyy.mm.dd hh24:mi:ss') hh,
2 to_char(trunc(sysdate,'mi'),'yyyy.mm.dd hh24:mi:ss') hhmm from dual;
HH HHMM
------------------- -------------------
2004.05.09 11:00:00 2004.05.09 11:17:00
42.CHARTOROWID
將字符數據類型轉換為ROWID類型
SQL> select rowid,rowidtochar(rowid),ename from scott.emp;
ROWID ROWIDTOCHAR(ROWID) ENAME
------------------ ------------------ ----------
AAAAfKAACAAAAEqAAA AAAAfKAACAAAAEqAAA SMITH
AAAAfKAACAAAAEqAAB AAAAfKAACAAAAEqAAB ALLEN
AAAAfKAACAAAAEqAAC AAAAfKAACAAAAEqAAC WARD
AAAAfKAACAAAAEqAAD AAAAfKAACAAAAEqAAD JONES
43.CONVERT(c,dset,sset)
將源字符串 sset從一個語言字符集轉換到另一個目的dset字符集
SQL> select convert('strutz','we8hp','f7dec') "conversion" from dual;
conver
------
strutz
44.HEXTORAW
將一個十六進制構成的字符串轉換為二進制
45.RAWTOHEXT
將一個二進制構成的字符串轉換為十六進制
46.ROWIDTOCHAR
將ROWID數據類型轉換為字符類型
47.TO_CHAR(date,'format')
SQL> select to_char(sysdate,'yyyy/mm/dd hh24:mi:ss') from dual;
TO_CHAR(SYSDATE,'YY
-------------------
2004/05/09 21:14:41
48.TO_DATE(string,'format')
將字符串轉化為ORACLE中的一個日期
49.TO_MULTI_BYTE
將字符串中的單字節字符轉化為多字節字符
SQL> select to_multi_byte('高') from dual;
TO
--
高
50.TO_NUMBER
將給出的字符轉換為數字
SQL> select to_number('1999') year from dual;
YEAR
---------
1999
51.BFILENAME(dir,file)
指定一個外部二進制文件
SQL>insert into file_tb1 values(bfilename('lob_dir1','image1.gif'));
52.CONVERT('x','desc','source')
將x字段或變量的源source轉換為desc
SQL> select sid,serial#,username,decode(command,
2 0,'none',
3 2,'insert',
4 3,
5 'select',
6 6,'update',
7 7,'delete',
8 8,'drop',
9 'other') cmd from v$session where type!='background';
SID SERIAL# USERNAME CMD
--------- --------- ------------------------------ ------
1 1 none
2 1 none
3 1 none
4 1 none
5 1 none
6 1 none
7 1275 none
8 1275 none
9 20 GAO select
10 40 GAO none
53.DUMP(s,fmt,start,length)
DUMP函數以fmt指定的內部數字格式返回一個VARCHAR2類型的值
SQL> col global_name for a30
SQL> col dump_string for a50
SQL> set lin 200
SQL> select global_name,dump(global_name,1017,8,5) dump_string from global_name;
GLOBAL_NAME DUMP_STRING
------------------------------ --------------------------------------------------
ORACLE.WORLD Typ=1 Len=12 CharacterSet=ZHS16GBK: W,O,R,L,D
54.EMPTY_BLOB()和EMPTY_CLOB()
這兩個函數都是用來對大數據類型字段進行初始化操作的函數
55.GREATEST
返回一組表達式中的最大值,即比較字符的編碼大小.
SQL> select greatest('AA','AB','AC') from dual;
GR
--
AC
SQL> select greatest('啊','安','天') from dual;
GR
--
天
56.LEAST
返回一組表達式中的最小值
SQL> select least('啊','安','天') from dual;
LE
--
啊
57.UID
返回標識當前用戶的唯一整數
SQL> show user
USER 為"GAO"
SQL> select username,user_id from dba_users where user_id=uid;
USERNAME USER_ID
------------------------------ ---------
GAO 25
58.USER
返回當前用戶的名字
SQL> select user from dual;
USER
------------------------------
GAO
59.USEREVN
返回當前用戶環境的信息,opt可以是:
ENTRYID,SESSIONID,TERMINAL,ISDBA,LABLE,LANGUAGE,CLIENT_INFO,LANG,VSIZE
ISDBA 查看當前用戶是否是DBA如果是則返回true
SQL> select userenv('isdba') from dual;
USEREN
------
FALSE
SQL> select userenv('isdba') from dual;
USEREN
------
TRUE
SESSION
返回會話標志
SQL> select userenv('sessionid') from dual;
USERENV('SESSIONID')
--------------------
152
ENTRYID
返回會話人口標志
SQL> select userenv('entryid') from dual;
USERENV('ENTRYID')
------------------
0
INSTANCE
返回當前INSTANCE的標志
SQL> select userenv('instance') from dual;
USERENV('INSTANCE')
-------------------
1
LANGUAGE
返回當前環境變量
SQL> select userenv('language') from dual;
USERENV('LANGUAGE')
----------------------------------------------------
SIMPLIFIED CHINESE_CHINA.ZHS16GBK
LANG
返回當前環境的語言的縮寫
SQL> select userenv('lang') from dual;
USERENV('LANG')
----------------------------------------------------
ZHS
TERMINAL
返回用戶的終端或機器的標志
SQL> select userenv('terminal') from dual;
USERENV('TERMINA
----------------
GAO
VSIZE(X)
返回X的大小(字節)數
SQL> select vsize(user),user from dual;
VSIZE(USER) USER
----------- ------------------------------
6 SYSTEM
60.AVG(DISTINCT|ALL)
all表示對所有的值求平均值,distinct只對不同的值求平均值
SQLWKS> create table table3(xm varchar(8),sal number(7,2));
語句已處理。
SQLWKS> insert into table3 values('gao',1111.11);
SQLWKS> insert into table3 values('gao',1111.11);
SQLWKS> insert into table3 values('zhu',5555.55);
SQLWKS> commit;
SQL> select avg(distinct sal) from gao.table3;
AVG(DISTINCTSAL)
----------------
3333.33
SQL> select avg(all sal) from gao.table3;
AVG(ALLSAL)
-----------
2592.59
61.MAX(DISTINCT|ALL)
求最大值,ALL表示對所有的值求最大值,DISTINCT表示對不同的值求最大值,相同的只取一次
SQL> select max(distinct sal) from scott.emp;
MAX(DISTINCTSAL)
----------------
5000
62.MIN(DISTINCT|ALL)
求最小值,ALL表示對所有的值求最小值,DISTINCT表示對不同的值求最小值,相同的只取一次
SQL> select min(all sal) from gao.table3;
MIN(ALLSAL)
-----------
1111.11
63.STDDEV(distinct|all)
求標準差,ALL表示對所有的值求標準差,DISTINCT表示只對不同的值求標準差
SQL> select stddev(sal) from scott.emp;
STDDEV(SAL)
-----------
1182.5032
SQL> select stddev(distinct sal) from scott.emp;
STDDEV(DISTINCTSAL)
-------------------
1229.951
64.VARIANCE(DISTINCT|ALL)
求協方差
SQL> select variance(sal) from scott.emp;
VARIANCE(SAL)
-------------
1398313.9
65.GROUP BY
主要用來對一組數進行統計
SQL> select deptno,count(*),sum(sal) from scott.emp group by deptno;
DEPTNO COUNT(*) SUM(SAL)
--------- --------- ---------
10 3 8750
20 5 10875
30 6 9400
66.HAVING
對分組統計再加限制條件
SQL> select deptno,count(*),sum(sal) from scott.emp group by deptno having count(*)>=5;
DEPTNO COUNT(*) SUM(SAL)
--------- --------- ---------
20 5 10875
30 6 9400
SQL> select deptno,count(*),sum(sal) from scott.emp having count(*)>=5 group by deptno ;
DEPTNO COUNT(*) SUM(SAL)
--------- --------- ---------
20 5 10875
30 6 9400
67.ORDER BY
用于對查詢到的結果進行排序輸出
SQL> select deptno,ename,sal from scott.emp order by deptno,sal desc;
DEPTNO ENAME SAL
--------- ---------- ---------
10 KING 5000
10 CLARK 2450
10 MILLER 1300
20 SCOTT 3000
20 FORD 3000
20 JONES 2975
20 ADAMS 1100
20 SMITH 800
30 BLAKE 2850
30 ALLEN 1600
30 TURNER 1500
30 WARD 1250
30 MARTIN 1250
30 JAMES 950
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