Select 语句
Select?語句大概可分為4部分
1．??主體部分
語法：select [distinct]<[*]|[字段列表]> from <表名>
功能：根據字段列表給出的列篩選出表名所指數據表的全部記錄，”*”表示全部字段,distinct表示篩選掉與該字段重復的記錄。
2．??條件部分
語法：where <條件表達式>
功能：根據條件表達式篩選出主體部分指定表滿足條件的記錄。
3．??排序部分
語法：order by <字段列表> [desc]
功能：根據字段列表給出的順序進行排序，desc代表到序。
4．??分組部分
語法:group by <字段列表>
功能：在利用select進行統計、匯總等工作的時候，可以對匯總內容進行分組，如：統計全局民警總數，用性別字段分組，這樣的到的結果就是男性總數、女性總數。
Select語句中的常用函數
Count()?? | 統計 |
Sum()??? | 匯總 |
?Max()??? | 最大值 |
Min()??? | 最小值 |
Avg()??? | 平均值 |
?Lenght()??? | 字符串長度 |
?Substr(字符串,起始位置，結束位置)? | 取子串 |
??decode(條件,值1,翻譯值1,值2,翻譯值2,...值n,翻譯值n,缺省值)? | 選擇 |
?To_char()? | 轉字符串 |
To_number()? | 轉數字 |
Select?語句運算符
1．???算術運算符
+ | 加 |
- | 減 |
* | 乘 |
/ | 除 |
2．??關系運算符
>? | 大于 |
<? | 小于 |
>= | 大于等于 |
<= | 小于等于 |
= | 等于 |
<>? | 不等于 |
?
3．??邏輯運算符
And | 與 |
Or | 或 |
Not | 非 |
?
Sql?其他函數(網絡資料)
SQL中的單記錄函數
1.ASCII?返回與指定的字符對應的十進制數;
SQL> select ascii('A') A,ascii('a') a,ascii('0') zero,ascii(' ') space from dual;A???????? A????? ZERO???? SPACE
--------- --------- --------- ---------
65??????? 97??????? 48??????? 32
2.CHR?給出整數,返回對應的字符;
SQL> select chr(54740) zhao,chr(65) chr65 from dual;
ZH C
-- -
趙?A
3.CONCAT?連接兩個字符串;
SQL> select concat('010-','88888888')||'轉23'??高乾競電話?from dual;
高乾競電話
----------------
010-88888888轉23
4.INITCAP?返回字符串并將字符串的第一個字母變為大寫;
SQL> select initcap('smith') upp from dual;
UPP
-----
Smith
5.INSTR(C1,C2,I,J)?在一個字符串中搜索指定的字符,返回發現指定的字符的位置;
C1????被搜索的字符串
C2????希望搜索的字符串
I?????搜索的開始位置,默認為1
J?????出現的位置,默認為1
SQL> select instr('oracle traning','ra',1,2) instring from dual;
INSTRING
---------
9
6.LENGTH?返回字符串的長度;
SQL> select name,length(name),addr,length(addr),sal,length(to_char(sal)) from .nchar_tst;
NAME?? LENGTH(NAME) ADDR???????????? LENGTH(ADDR)?????? SAL LENGTH(TO_CHAR(SAL))
------ ------------ ---------------- ------------ --------- --------------------
高乾競??????????? 3?北京市海錠區??????????????? 6?? 9999.99??????????????????? 7
7.LOWER?返回字符串,并將所有的字符小寫
SQL> select lower('AaBbCcDd')AaBbCcDd from dual;
AABBCCDD
--------
aabbccdd
8.UPPER?返回字符串,并將所有的字符大寫
SQL> select upper('AaBbCcDd') upper from dual;
UPPER
--------
AABBCCDD
9.RPAD和LPAD(粘貼字符)
RPAD??在列的右邊粘貼字符
LPAD??在列的左邊粘貼字符
SQL> select lpad(rpad('gao',10,'*'),17,'*')from dual;
LPAD(RPAD('GAO',1
-----------------
*******gao*******
不夠字符則用*來填滿
10.LTRIM和RTRIM
LTRIM??刪除左邊出現的字符串
RTRIM??刪除右邊出現的字符串
SQL> select ltrim(rtrim('?? gao qian jing?? ',' '),' ') from dual;
LTRIM(RTRIM('
-------------
gao qian jing
11.SUBSTR(string,start,count)
取子字符串,從start開始,取count個
SQL> select substr('13088888888',3,8) from dual;
SUBSTR('
--------
08888888
12.REPLACE('string','s1','s2')
string???希望被替換的字符或變量?
s1???????被替換的字符串
s2???????要替換的字符串
SQL> select replace('he love you','he','i') from dual;
REPLACE('HELOVEYOU','HE','I')
------------------------------
i love you
13.SOUNDEX?返回一個與給定的字符串讀音相同的字符串
SQL> create table table1(xm varchar(8));
SQL> insert into table1 values('weather');
SQL> insert into table1 values('wether');
SQL> insert into table1 values('gao');
SQL> select xm from table1 where soundex(xm)=soundex('weather');
XM
--------
weather
wether
14.TRIM('s' from 'string')
LEADING???剪掉前面的字符
TRAILING??剪掉后面的字符
如果不指定,默認為空格符
15.ABS?返回指定值的絕對值
SQL> select abs(100),abs(-100) from dual;
ABS(100) ABS(-100)
--------- ---------
100?????? 100
16.ACOS?給出反余弦的值
SQL> select acos(-1) from dual;
ACOS(-1)
---------
3.1415927
17.ASIN?給出反正弦的值
SQL> select asin(0.5) from dual;
ASIN(0.5)
---------
.52359878
18.ATAN?返回一個數字的反正切值
SQL> select atan(1) from dual;
ATAN(1)
---------
.78539816
19.CEIL?返回大于或等于給出數字的最小整數
SQL> select ceil(3.1415927) from dual;
CEIL(3.1415927)
---------------
4
20.COS?返回一個給定數字的余弦
SQL> select cos(-3.1415927) from dual;
COS(-3.1415927)
---------------
-1
21.COSH?返回一個數字反余弦值
SQL> select cosh(20) from dual;
COSH(20)
---------
242582598
22.EXP?返回一個數字e的n次方根
SQL> select exp(2),exp(1) from dual;
EXP(2)??? EXP(1)
--------- ---------
7.3890561 2.7182818
23.FLOOR?對給定的數字取整數
SQL> select floor(2345.67) from dual;
FLOOR(2345.67)
--------------
2345
24.LN?返回一個數字的對數值
SQL> select ln(1),ln(2),ln(2.7182818) from dual;
LN(1)???? LN(2) LN(2.7182818)
--------- --------- -------------
0 .69314718???? .99999999
25.LOG(n1,n2)?返回一個以n1為底n2的對數?
SQL> select log(2,1),log(2,4) from dual;
LOG(2,1)? LOG(2,4)
--------- ---------
0???????? 2
?
26.MOD(n1,n2)?返回一個n1除以n2的余數
SQL> select mod(10,3),mod(3,3),mod(2,3) from dual;
MOD(10,3)? MOD(3,3)? MOD(2,3)
--------- --------- ---------
1???????? 0???????? 2
27.POWER?返回n1的n2次方根
SQL> select power(2,10),power(3,3) from dual;
POWER(2,10) POWER(3,3)
----------- ----------
1024???????? 27
28.ROUND和TRUNC
按照指定的精度進行舍入
SQL> select round(55.5),round(-55.4),trunc(55.5),trunc(-55.5) from dual;
ROUND(55.5) ROUND(-55.4) TRUNC(55.5) TRUNC(-55.5)
----------- ------------ ----------- ------------
56????????? -55????????? 55????????? -55
29.SIGN?取數字n的符號,大于0返回1,小于0返回-1,等于0返回0
SQL> select sign(123),sign(-100),sign(0) from dual;
SIGN(123) SIGN(-100)?? SIGN(0)
--------- ---------- ---------
1???????? -1???????? 0
30.SIN?返回一個數字的正弦值
SQL> select sin(1.57079) from dual;
SIN(1.57079)
------------
1
31.SIGH?返回雙曲正弦的值
SQL> select sin(20),sinh(20) from dual;
SIN(20)? SINH(20)
--------- ---------
.91294525 242582598
32.SQRT?返回數字n的根
SQL> select sqrt(64),sqrt(10) from dual;
SQRT(64)? SQRT(10)
--------- ---------
8 3.1622777
33.TAN?返回數字的正切值
SQL> select tan(20),tan(10) from dual;
TAN(20)?? TAN(10)
--------- ---------
2.2371609 .64836083
34.TANH
返回數字n的雙曲正切值
SQL> select tanh(20),tan(20) from dual;
TANH(20)?? TAN(20)
--------- ---------
1 2.2371609
35.TRUNC
按照指定的精度截取一個數
SQL> select trunc(124.1666,-2) trunc1,trunc(124.16666,2) from dual;
TRUNC1 TRUNC(124.16666,2)
--------- ------------------
100???????????? 124.16
36.ADD_MONTHS
增加或減去月份
SQL> select to_char(add_months(to_date('199912','yyyymm'),2),'yyyymm') from dual;
TO_CHA
------
200002
SQL> select to_char(add_months(to_date('199912','yyyymm'),-2),'yyyymm') from dual;
TO_CHA
------
199910
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.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','p_w_picpath1.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 nt(*)>=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 tno ;
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
轉載于:https://blog.51cto.com/6226001001/1595638
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