TO_CHAR(<x> [,<fmt >[,<nlsparm>] ])
SELECT TO_CHAR(SYSDATE,'Day Ddspth,Month YYYY'
,'NLS_DATE_LANGUAGE=German') Today_Heute
FROM dual;
SELECT TO_CHAR(SYSDATE
,'"On the "Ddspth" day of "Month, YYYY')
FROM dual;
这里的Dd和DD意思一样，不同点是单词首字母大写，其他小写
TO_CHAR(SYSDATE,'"ONTHE"DDSPTH"DAYOF"MONTH,Y
--------------------------------------------
On the Twenty-Seventh day of November , 2002
SP 数字的拼写 ---spelling out
TH 数字的序数词
spth 使用序数词来拼写，如12--->twelve(sp方式) -->Twelfth (spth方式)
SELECT SYSDATE
,TO_CHAR(SYSDATE,'Mmspth') Month
,TO_CHAR(SYSDATE,'DDth') Day
,TO_CHAR(SYSDATE,'Yyyysp') Year
FROM dual;
SYSDATE MONTH DAY YEAR
----------- -------- ---- -------------------------------------
01-DEC-1999 Twelfth 01ST One Thousand Nine Hundred Ninety-Nine
其中01ST是数字的序数词，Twelfth 是数字被拼写后的序数词
Yyyy就是YYYY，但是每个单词首字母大写，其他小写
SELECT TO_CHAR(SYSDATE,'MONTH') upperCase
,TO_CHAR(SYSDATE,'Month') mixedCase
,TO_CHAR(SYSDATE,'month') lowerCase
FROM dual;
UPPERCASE MIXEDCASE LOWERCASE
--------- --------- ---------
DECEMBER December december
Date Format Codes
Date Code | Format Code Description | Example
AD or BC Epoch indicator ‘YYYY AD’ = 2002 AD
A.D. or B.C. Epoch indicator with periods ‘YYYY A.D.’ = 2002 A.D.
AM or PM Meridian indicator ‘HH12AM’ = 09AM
A.M. or P.M. Meridian indicator with periods ‘HH A.M.’= 09 A.M.
DY Day of week abbreviated Mon, Tue, Fri
DAY Day of week spelled out Monday, Tuesday, Friday
D Day of week (1–7) 1,2,3,4,5,6,7
DD Day of month (1–31) 1,2,3,4…31
DDD Day of year (1–366) 1,2,3,4…366
FF Fractional seconds .34127
J Julian day (days since 4712BC) 2451514,2451515,2451516
W Week of the month (1–5) 1,2,3,4,5
WW, IW Week of the year, ISO week of the year 1,2,3,4…53
MM Two-digit month 01,02,03…12
MON Month name abbreviated Jan, Feb, Mar…Dec
MONTH Month name spelled out January, February…
Q Quarter 01-Jan-2002
RM Roman numeral month (I–XII) I,II,III,IV,V…XII
YYYY,YYY, Four-digit year; last 3, 2, 1 1999, 999, 99, 9
YY, Y digits in the year 2000, 000, 00, 0
YEAR Year spelled out Two thousand two
SYYYY If BC, year is shown as negative -1250
RR Used for data input with only See description
two digits for the year following table
HH, HH12 Hour of the half-day (1–12) 1,2,3…12
HH24 Hour of the day (0–23) 0,1,2…23
MI Minutes of the hour (0–59) 0,1,2…59
SS Seconds of the minute (0–59) 0,1,2…59
SSSSS Seconds of the day (0–86399) 0,1,2…86399
TZD Time zone daylight savings; CST
must correspond to TZR
TZH Time zone hour, together 07
with TZM is time zone offset
TZM Time zone minute, together 00
with TZH is time zone offset
TZR Time zone region US/Central, Mexico/BajaNorte
, . / - ; : Punctuation Literal display
‘text’ Quoted text Literal display
SELECT TO_CHAR(123456,'9.99EEEE')
,TO_CHAR(123456,'9.9EEEE')
FROM dual;
TO_CHAR(12 TO_CHAR(1
---------- ---------
1.23E+05 1.2E+05
SELECT TO_CHAR(-1234.56,'C099G999D99MI','NLS_NUMERIC_CHARACTERS='',.''
NLS_CURRENCY=''DM''NLS_ISO_CURRENCY=''GERMANY''') Balance
FROM dual;
BALANCE
--------------
DEM001.234,56-
其中C 代表使用ISO international currency symbol (format symbol C).
For example, the NLS_CURRENCY symbol for U.S. dollars is $, but this
symbol is not uniquely American, so the ISO symbol for U.S. dollars is USD.
Numeric
Code|Format Code Description |Example
9 Numeric digits with leading space if 9999.9 = 1234.5
positive and a leading – (minus) if 9999.9 = -1234.5
negative. 9999.9 = .3
0 Leading and/or trailing zeros. 0009.90 = 0012.30
代表一位数字，在相应的位置上如果没有数字则出现0
, Comma, for use as a group separator. 9,999.9 = 1,234.5
It cannot appear after a period or
decimal code.
G Local group separator, could be comma 9G999D9 = 1,234.5
(,) or period (.). 9G999D9 = 1.234,5
分组分隔符（使用本地化）
. Period, for use as the decimal character. 9,999.9 = 1,234.5
It cannot appear more than once or to
the left of a group separator.
D Local decimal character, could be 9G999D9 = 1,234.5
comma (,) or period (.). 9G999D9 = 1.234,5
小数点（使用本地化）
$ Dollar-sign currency symbol. $999 = $123
L Local currency symbol. L999 = $123
L999 = Euro123
FM No leading or trailing blanks. FM99.99 = .1
EEEE Scientific notation. 9.9EEEE = 1.2E+05
MI Negative as a trailing minus. 999MI = 137-
PR Negative in angle brackets (< >). 999PR = <137>
S Negative as a leading minus. S999 = -137
S:负数符号−放在开头,如:S999.9
RN Uppercase Roman numeral. RN = XXIV
rn Lowercase Roman numeral. rn = xxiv
X Hexadecimal XX = FC
-------------------------------------------------------------
Oracle聚合函数RANK和dense_rank的使用
唯一区别就是如果排名重复rank则跳过，如 1，2，2，4
dense_rank则不跳过： 如1,2,2,3
TABLE：A （科目，分数）
数学，80
语文，70
数学，90
数学，60
数学，100
语文，88
语文，65
语文，77
现在我想要的结果是：（即想要每门科目的前3名的分数）
数学，100
数学，90
数学，80
语文，88
语文，77
语文，70
那么语句就这么写：
select * from (select rank() over(partition by 科目 order by 分数 desc) rk,a.* from a) t
where t.rk<=3;
例子3：
合计功能：计算出数值(4,1)在Orade By Col1,Col2排序下的排序值，也就是col1=4,col2=1在排序以后的位置
SELECT RANK(4,3) WITHIN GROUP (ORDER BY col1,col2) "Rank" FROM table;
结果如下：
Rank
4
dense_rank与rank()用法相当，但是有一个区别：dence_rank在并列关系是，相关等级不会跳过。rank则跳过
例如：表
A B C
a liu wang
a jin shu
a cai kai
b yang du
b lin ying
b yao cai
b yang 99
例如：当rank时为：
select m.a,m.b,m.c,rank() over(partition by a order by b) liu from test3 m
A B C LIU
a cai kai 1
a jin shu 2
a liu wang 3
b lin ying 1
b yang du 2
b yang 99 2
b yao cai 4
而如果用dense_rank时为：
select m.a,m.b,m.c,dense_rank() over(partition by a order by b) liu from test3 m
A B C LIU
a cai kai 1
a jin shu 2
a liu wang 3
b lin ying 1
b yang du 2
b yang 99 2
b yao cai 3
------------------------------------------------------------------
rollup----如果是ROLLUP(A, B, C)的话,则先group by (a,b,c)--->group by(a,b) -->group by (a)-->group by (全表)
cube---->如果是GROUP BY CUBE(A, B, C)，则首先会对(A、B、C)进行GROUP BY，然后依次是(A、B)，(A、C)，(A)，(B、C)，(B)，(C)，最后对全表进行GROUP BY操作。
