Oracle date format conversion to_ date,to_ char,to_ Timestamp mutual conversion

Oracle Date format conversion to_date,to_char,to_timetamp transformation

One 、 summary

        1、 Main records of this paper Oracle In the database , Common date format conversion . Use to_char function , Convert date to string ; Use to_date 、to_timetamp function , Convert the string to the corresponding date type .

        2、Oracle The database version is ：Oracle 11g.

Two 、 Date conversion string to_char

        1、 frequently-used 2 A date function ：SYSDATE , SYSTIMESTAMP

SELECT SYSDATE , SYSTIMESTAMP FROM dual ;

 

        2、SYSDATE Turn the string

SELECT
	SYSDATE 
, TO_CHAR(SYSDATE, 'yyyy-mm-dd hh:mm:ss') AS "h12" -- 12 hourly 
, TO_CHAR(SYSDATE, 'yyyy-mm-dd hh24:mi:ss') AS "h24" -- 24 The hour system 
FROM dual ;

 

        3、SYSTIMESTAMP Turn the string

SELECT 
	SYSTIMESTAMP  
	, TO_CHAR(SYSTIMESTAMP, 'yyyy-mm-dd hh24:mi:ss') AS "h24" -- 24 Hours 
	, TO_CHAR(SYSTIMESTAMP, 'yyyy-mm-dd hh24:mi:ss.ff3') AS "h24mi" -- 24 Hours mi
FROM
	dual ;

 

 

        4、SYSDATE Common conversion

SELECT
	TO_CHAR(SYSDATE , 'yyyy') AS  year  ,
	TO_CHAR(to_date('2022-07-01', 'yyyy-mm-dd'), 'q') AS  quarter  ,
	TO_CHAR(SYSDATE , 'mm') AS  month  ,
	TO_CHAR(SYSDATE  , 'dd') AS  Japan , --  The day of the month 
	TO_CHAR(SYSDATE  , 'd') AS " Japan （ Zhou ）", --  What day of the week （ The first day is Sunday ）
	TO_CHAR(SYSDATE  , 'ddd') AS " Japan （ year ）" , --  What day of the year 
	TO_CHAR(SYSDATE  , 'ww') AS " Zhou （ year ）", --  The weeks of the year 
	TO_CHAR(to_date('2022-01-08', 'yyyy-mm-dd')  , 'ww') AS " Zhou （ year ）" --  The weeks of the year 
FROM
	dual ;

 

3、 ... and 、 String to date

        1、to_date String rotation date ：

SELECT
	TO_DATE('2022-06-20 17:08:06' , 'yyyy-mm-dd hh24:mi:ss') AS "date"
FROM
	dual ;

        2、TO_TIMESTAMP String rotation date ：

SELECT
	TO_TIMESTAMP('2022-06-20 17:08:06.114', 'yyyy-mm-dd hh24:mi:ss.ff3') AS "t1"
  ,	TO_TIMESTAMP('2022-06-20 17:08:06', 'yyyy-mm-dd hh24:mi:ss') AS "t1"
FROM
	dual ;

 

Four 、 summary

        1、Oracle in , Date to string ： Use to_char Function , but to_char Function also supports more format conversions , The parameters you can refer to are as follows ：

【 The first parameter is a numeric type 】

Serial number	Format	A brief example	explain
1	,( comma )	'9999,999'	comma , It usually appears in the thousandth place , Used as a grouping symbol . If you need to, you can also take it as a tenth , The percentile appears , Can appear N Time , It depends on the size of the number .
			An example of perversion is to_char(1234,'9,9,9,9').
			matters needing attention : Can only appear in the integral part .
2	.( Order number )	'99.99'	Order number , Don't read it as " Full stop ", A full stop is a circle , A good point can only appear in the place corresponding to the decimal point . Only once .
			to_char(1234.34,'9,9,9,9.99')
			matters needing attention : Only in one place , It's the decimal point of the original data
3	$( Dollar symbol )	'$999.99'	dollar . You can actually put it anywhere ( stay 10G Next )
			to_char(1234.34,'9,9,9,9.$99')
			matters needing attention : Only once .
4	0( zero )	'0999.99'	zero . Returns the corresponding character in the corresponding position , If not, take '0' fill .
			to_char(0.34,'9,9,9,0.$99')='$0.34';to_char(1234,'9999.00')='1234.00';
			matters needing attention : It's a mandatory symbol , There is no corresponding bit , with 'o' fill , This is a 9 It's very different
5	9	'999.99'	9. In decimal places , It means to convert to the corresponding character , If not, take 0 Express ; In the whole number , If there is no correspondence, the characters will not be filled .
			to_char(123,'999.99')=123.00; TO_CHAR(123,'99999.9')=123.0;
			matters needing attention : about 0 and 9 for , If the number of digits in the format is less than the number of digits in the number , Returns the '#'.
			for example to_char(12345,'9999')='#####'
6	B( Space character )	'B999'	No other special effect , Add a space to the front of the integer part , Can appear anywhere .
			'S'||TO_CHAR(1234,'99B99')='S 1234';
			matters needing attention : It can only appear in the integer part .
7	C( International currency symbol )	'C9999'	Returns a... At a specific location ISO Currency symbols ( Namely NLS_ISO_CURRENCY The value represented by the parameter )
			TO_CHAR(1233,'C9999')='CNY1234' , This is a new international standard RMB, You can find out about this " International currency symbol "
			matters needing attention : It can only appear in the first digit of the integer part .
			Can pass alter session set NLS_ISO_CURRENCY='JAPAN'; To modify the settings of the current session .
8	D(ISO Decimal symbols )	'999D99'	This is a " Order number " International version of (ISO), It's equivalent to a point , It can only appear once . The difference is , The database will be based on NLS_NUMERIC_CHARACTER To set the content . The default value is the dot .
			matters needing attention : There is no special need. Generally, do not use this format symbol . Don't change the parameter value easily .
			Also available alter sesssion set To modify the .
			alter session set nls_numeric_characters='!,';   to_char(1234.34,'9999d99')=1234!34
9	EEEE( Scientific operators )	9.9EEEE	Scientific computing symbols
			TO_CHAR(2008032001,'9.9EEEE')='2.01E+09', Because it's a scientific calculation method , So add one before the decimal 9 perhaps 0 that will do , There's no point in having more than one .
10	G( Grouping symbols )	999G999	It's a comma (,) Of course ISO standard , Used as a grouping symbol , It can be used in many places .
			TO_CHAR(123456,'999G9G99')=123,4,56
			matters needing attention : Same as item 8 -D, In addition, if you want to convert the decimal point , It's going to be with D In combination with , Can't match the point number .
11	L( Local currency symbol )	'L999'	yes C Local version of . It can be placed at the front and back of the whole format .
			TO_CHAR(123456,'999G9G99D00L')=123,4,56.00￥
			matters needing attention : Same as item 7 C
12	MI( Minus sign )	'9999MI'	If it's a negative number , Put a minus sign at the end (-), If it's a positive number , Then add a space to the tail
			to_char(1234,'9999mi')||'S'||TO_CHAR(-5678,'9999MI') =1234 S5678-
			matters needing attention : Can only be placed at the end of the format
13	PR( Symbol )	9999PR	It's another way to express negative numbers . If it's a positive number , Then add a space to the head ; If it's a negative number , Use parentheses <> Wrap up the numbers .
			TO_CHAR(-1234.89,'9G999D00PR')=<1,234.89>
			matters needing attention : Same as 12
14	RN(rn)	RN(rn)	Integer (1-3999) Convert to Roman .RN Turn to capital ,rn It means lowercase .
			declare
			i int;
			begin
			for i in 1..20 loop
			dbms_output.put_line(to_char(i,'RN'));
			end loop;
			end;
			matters needing attention : You can only use , Cannot be used in combination with other symbols .
15	S	'9999S'	yes 12,13 A comprehensive and improved version of . Add a positive sign to an integer +, Add a sign to a negative number -.S In the front, add in the front , After, after .
			TO_CHAR(-1234,'S9999')=-1234;TO_CHAR(1234,'S9999')=+1234
16	TM	TM9/TMe	To use this parameter is to use no parameter to_char(number) equally , Should be 'tm9' Is the default format parameter .
			to_char(1234,'tme')=1234
			matters needing attention : The format is either TM9, Or TME.
			When the number length exceeds 64 At the same time ,TM9 The output of is equivalent to TME Output .
17	U	U999	Double Coin symbol , For example, the euro . Work with 11 Of L
			TO_CHAR(999,'U999')=￥999
			matters needing attention ： adopt NLS_DUAL_CURRENCY control
18	V	999V9	It's a little weird , It's not a very common symbol . Its purpose is to do a calculation .
			for example TO_CHAR(N,'999V9'), With p Express V The location of , Then the expression ＝to_char(N×(10 Of P-1 Power )). however 9 The number must be greater than or equal to the number of digits after the product .
			TO_CHAR(5,'9V')=5*1=5;
			TO_CHAR(5,'9V9')=5*10=50
			TO_CHAR(5,'9V99')=500
			TO_CHAR(50,'9V99')='######' 9 There are not enough of them
			matters needing attention ： The format cannot be written with decimal expression , But you can mix currencies and so on .
19	X	xxxx	Convert to 16 Base number .
			TO_CHAR(100,'XX')= 64
			matters needing attention ： The value must be greater than or equal to 0 The integer of . The front can only be connected with 0 perhaps FM Use a combination of .
20			Through the above example , We learned about the formats of various numbers . It can be said that there are too many formats , It's hard to remember , It's best to exist as a reference .
			classified ：
			Numerical class ： 0,9,
			Grouping classes ： (.),(,),D,G , There's a dot good and a comma because it's not obvious , So use parentheses to highlight .
			Currency ：　$,C,L,U
			Compute transformation class ：EEEE,RN,V,X
			Positive and negative signs ：MI,PR,S
			Other classes ：B
			Orthodox class ：TM

【 The first parameter is zero ： Date type 】

Serial number	Format	A brief example	explain
1	- / , . ; :	A little	The time separator , Except for the standard ones , Text is also allowed as a segmentation symbol .
	"text"		for example to_char(sysdate,'YYYY" year "mm" month "dd" Japan "')=2008 year 04 month 24 Japan
2	AD		Latin Anno Domini Abbreviation , It means A.D . Will be based on nls The difference between A.D. and A.D ad etc.
	A.D.		No special considerations
3	AM		Short for morning , Same as pm, p.m. （ Afternoon ) , The output of Chinese environment is in the morning （ If it's morning ）
	A.M.
4	BC		Although the standard writing is B.c. (c A lowercase letter ） perhaps BC, Fortunately Oracle I don't care about this . B.C
	B.C.
5	CC		Back in the century , In Arabic numerals
	SCC		If the last two places of the year are between 01-99 that , Back to the top two +1, Otherwise go back to the top two
6	D		One day of the week , It returns the serial number 1-7
7	DAY		One day of the week , But it's just the day of the week , It has to do with language settings , In the Chinese environment NLS_DATE_LANGUAGE=SIMPLIFIED CHINESE , From Monday to Sunday
8	DD		One day in the month (1-31)
9	DDD		One day in the year （1-366）
10	DL	'DL'	Returns the long date format . suffer NLS_TERRITORY,NLS_LANGUAGE Parameter control . example 2008 year 4 month 28 Japan Monday
			Limit ： except DL, Nothing else can be set .
11	DS		Returns the short date format . suffer NLS_TERRITORY,NLS_LANGUAGE Parameter control . for example 2008-04-28
			Limit ： except DL, Nothing else can be set .
12	DY		Abbreviation of date , It's the day of the week （ Of course, this refers to the Chinese environment )
13	E		Era is short for , But only for the following centralized calendars ： The Japanese royal family , Republic of China , Too much Buddhist calendar
14	EE		The whole journey of the era , Suitable for the situation E
15	FF [1..9]		It's milliseconds , If you don't change the number, you use the default precision .
			It can only be used for timestamp Type of .
16	FM		A function worth noting ： Don't return anything .
			I don't understand oracle Why set this thing .
17	FX		ditto
18	HH		For hours , by 12 hourly , Same as hh12(1-12)
19	HH12		For hours , by 12 hourly (1-12)
20	HH24		For hours , by 24 hourly （0-23）
21	IW		ISO Standard week number (1-52, perhaps 1-53）
22	IYYY		IYY,IY,I, ISO year (4 position ） Of 4,3,2,1 Digit number ( Reciprocal ）
	IYY		to_char(to_date(21120401,'yyyymmdd'),'iyyy, iyy,iy,i')=2112, 112,12,2
	IY
	I
23	J		Julian day ( A calendar often used in astronomy ）, From b.c. 4712 From January 1, 2008 , The result is an integer , The algorithm is basically （ The date of A.D +4712）* Julian calendar year average days
24	MI		second （0-59）
25	MM		2 A month （1-12）
26	MON		The abbreviation of the month , It has something to do with the country NLS_DATE_LANGUAGE, for example 04 Using in Chinese environment 4 Monthly representation .
27	MONTH		The name of the month , The country has something to do with NLS_DATE_LANGUAGE, Now in Chinese 04 Expressed as 4 month .
28	PM		Same as am,a.m. In the afternoon
	P.M.
29	Q		quarter （1-4）
30	RM		The month in Roman numerals ,I   ,II ,III ,IV ,V   ,VI ,VII ,VIII,IX ,X   ,XI ,XII
31	RR		It's a bit of a round off for years , The specific usage is a little complicated .
			With s Represents the last two digits of the year entered ,c Represents the last two digits of the current year , Its output ( The top two in the new year ） You can use functions r=f(s,c) To express ,s2,c2 respectively s,c The first two of .
			1）s=[0,49],c=[0,49], be r=c2
			2) s=[0,49],c=[50,99], be r=c2+1
			3) s=[50,99],c=[0,49], be r=c2-1
			4) s=[50,99],c=[50,99], be r=c2
			In short, the principle of being close to the current year , If it's in the same region as the current year, then it's the same , If it's larger than the current area , Then it is regarded as the current century and the previous century , Otherwise it will be the next century .
			for instance , With to_date As an example
			SQL> select to_date('89-01-01','rr-mm-dd') ,to_date('12-01-01','rr-mm-dd') FROM DUAL;
			TO_DATE('89-01-01','RR-MM-DD') TO_DATE('12-01-01','RR-MM-DD')
			------------------------------ ------------------------------
			1989-01-01                     2012-01-01
			I think oracle I'm going to do this , It is estimated that there are two considerations. One is for convenience , One is to deal with a century or a millennium problem .
32	RRRR		If the input parameter has only two digits , Same with rr, Otherwise, it will be the same as yyyy effect .
33	SS		second （0-59）, In a minute
34	SSSSS		The cumulative number of seconds a day from midnight .(0-86399)
35	TS		Return short date format content , Including hours, minutes, seconds, etc , And the only dl,ds Use a combination of , The format is :
			dl ts perhaps dl ts , The middle is separated by a space .TO_CHAR(SYSDATE,'TS')= Afternoon 4:50:04
			Form is affected by NLS_TERRITORY and NLS_LANGUAGE influence .
36	TZD		Daylight saving time information , Time zone abbreviation plus daylight saving time information , Must be consistent with format tzr The set time zone corresponds to .
			Including the following three TZ At the beginning , It's all about time zones , Not directly for to_char
37	TZH		Hours in a time zone , for example hh:mi:ss.fftzh:tzm'
38	TZM		Minutes in the time zone .
39	TZR		Area information in the time zone , It must be a database supported time zone , for example US/Pacific
40	WW		and iw similar , It's also the serial number of the week , From the first day of the year to the last seventh day of the year . The two values are basically the same .（1-53） , for example 2008-01-01 To 2008-01-07 count 1,2008-01-09~2008-01-13 count 2
41	W		The week of the month , The algorithm is the same as ww, It's just limited to one month , and iso Different .
42	X		Represents the local root symbol , It's not particularly useful , And the only timestamp Type used together .
43	Y,YYY		Four years , It's good to separate them for example 2,008
44	YEAR		The year of articulation , for example 2008=two thousand eight
	SYEAR		S The prefix means B.C BC
45	YYYY		Four years ,S The prefix means B.C BC
	SYYYY
46	YYY		One time for the back 3,2,1 The year of a bit , for example 2008 It can be taken as 008,08,8
	YY
	Y
	summary		From the above , It is mainly the format of several parts of time ： century 、 year , month , Japan , when , branch , second , millisecond , And other mixed formats . Every part of time can be expressed in many ways , It's easier to remember by classifying in this way .
			Many formats can be combined , In this way, we can finally form a rich enough expression of its situation ;
			Secondly, a lot of formats and nls Is closely related ; Finally, some outputs （ return ） It has something to do with format case , This is not reflected in the Chinese environment （ I haven't seen it so far ）, however english Under the circumstances, under the name of , With to_char(sysdate,'day') As an example , If it's a western language environment, it's a return sun( hypothesis sysdate On weekends ）, If to_char(sysdate,'DAY') Then return to SUN

        2、 Be careful ：SYSDATE , SYSTIMESTAMP The time precision of the function is different ;SYSDATE Accurate to seconds ; SYSTIMESTAMP It can be accurate to seconds 6 position .