Conversioni Functionsi
Datatype conversion
Implicit datatype |
Explicit datatype |
conversion |
conversion |
3-22
ImplicitI li it Datatype Conversioni
For assignments, Oracle can automatically convert
From |
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To |
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VARCHAR2 or CHAR |
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NUMBER |
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VARCHAR2 or CHAR |
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DATE |
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NUMBER |
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VARCHAR2 |
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DATE |
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VARCHAR2 |
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3-23
ImplicitI li it Datatype Conversioni
For expression evaluation, Oracle can automatically convert
From |
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To |
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VARCHAR2 or CHAR |
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NUMBER |
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VARCHAR2 or CHAR |
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DATE |
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3-24
Explicitli it Datatype Conversioni
TO_NUMBER TO_DATE
NUMBER |
CHARACTER |
DATE |
TO_CHAR TO_CHAR
3-25
TO_CHAR Functioni withi Dates
TO_CHAR(date, 'fmt')
The formatf r t modell::
•• Mustt be enclosedl inin singlei le quotationt ti marksr and isis case sensitiveiti
•• Can includei l any validlid datete formatf r t elementl t
•• Has an fmfm elementl t toto remover padded blanksl orr suppressr leadingl i zerosr
•• IsIs separatedr t fromfr thet datete valuel by a comma
3-26
Date Format Modell Elementsl
YYYY |
Full year in numbers |
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YEAR |
Year spelled out |
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MM |
2-digit value for month |
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MONTH |
Full name of the month |
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DY |
3-letter abbreviation of the day |
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of the week |
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DAY |
Full name of the day |
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3-27
Date Format Modell Elementsl
•Time elements format the time portion of the date.
HH24:MI:SS AM |
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15:45:32 PM |
•Add character strings by enclosing them in double quotation marks.
DD "of" MONTH |
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12 of OCTOBER |
• Number suffixes spell out numbers.
ddspth |
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fourteenth |
3-28
Usingi TO_CHAR Functioni
withi Dates
SQL> SELECT ename,
2 TO_CHAR(hiredate, 'fmDD Month YYYY') HIREDATE
3 FROM emp;
ENAME |
HIREDATE |
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---------- |
----------------- |
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KING |
17 |
November 1981 |
BLAKE |
1 |
May 1981 |
CLARK |
9 |
June 1981 |
JONES |
2 |
April 1981 |
MARTIN |
28 |
September 1981 |
ALLEN |
20 |
February 1981 |
... |
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14 rows selected.
3-29
TO_CHAR Functioni withi Numbers
TO_CHAR(number, 'fmt')
Use these formats with the TO_CHAR function to display a number value as a character.
9Represents a number
0 Forces a zero to be displayed
$Places a floating dollar sign
L Uses the floating local currency symbol
.Prints a decimal point
,Prints a thousand indicator
3-30
Usingi TO_CHAR Functioni
withi Numbers
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SQL> |
SELECT |
TO_CHAR(sal,'$99,999') SALARY |
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2 |
FROM |
emp |
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3 |
WHERE |
ename = 'SCOTT'; |
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SALARY
--------
$3,000
3-31