Size of datatype number
what happens if i don't specify a size of a "number"-column?
in oracle database concepts i found this:
"If a precision is not specified, the column stores values as given. If no scale is specified, the scale is zero."
could someone explain me this a littlebit more please? what means zero? does this mean maximum?
thanks
Oracle stores numbers as a binary value in the range of:
Positive numbers in the range 1 x 10-130 to 9.99..9 x 10125 with up to 38 significant digits
Negative numbers from -1 x 10-130 to 9.99..99 x 10125 with up to 38 significant digits.
Each number is stored in scientific notation with Oracle using 1 byte to store the exponent and up to 20 bytes to store the value.
For more information refer to:
http://download-west.oracle.com/docs/cd/A87860_01/doc/server.817/a76965/c10datyp.htm#743
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Difference between datatype NUMBER and NUMBER(38)
Difference between datatype NUMBER and NUMBER(38)
From
http://download.oracle.com/docs/cd/B19306_01/server.102/b14200/sql_elements001.htm#i54330
NUMBER Datatype
The NUMBER datatype stores zero as well as positive and negative fixed numbers with absolute values from 1.0 x 10-130 to (but not including) 1.0 x 10126. If you specify an arithmetic expression whose value has an absolute value greater than or equal to 1.0 x 10126, then Oracle returns an error. Each NUMBER value requires from 1 to 22 bytes.
Specify a fixed-point number using the following form:
NUMBER(p,s)
where:
p is the precision, or the total number of significant decimal digits, where the most significant digit is the left-most nonzero digit, and the least significant digit is the right-most known digit. Oracle guarantees the portability of numbers with precision of up to 20 base-100 digits, which is equivalent to 39 or 40 decimal digits depending on the position of the decimal point.
s is the scale, or the number of digits from the decimal point to the least significant digit. The scale can range from -84 to 127.
Positive scale is the number of significant digits to the right of the decimal point to and including the least significant digit.
Negative scale is the number of significant digits to the left of the decimal point, to but not including the least significant digit. For negative scale the least significant digit is on the left side of the decimal point, because the actual data is rounded to the specified number of places to the left of the decimal point. For example, a specification of (10,-2) means to round to hundreds.
Scale can be greater than precision, most commonly when e notation is used. When scale is greater than precision, the precision specifies the maximum number of significant digits to the right of the decimal point. For example, a column defined as NUMBER(4,5) requires a zero for the first digit after the decimal point and rounds all values past the fifth digit after the decimal point.
It is good practice to specify the scale and precision of a fixed-point number column for extra integrity checking on input. Specifying scale and precision does not force all values to a fixed length. If a value exceeds the precision, then Oracle returns an error. If a value exceeds the scale, then Oracle rounds it.
Specify an integer using the following form:
NUMBER(p)
This represents a fixed-point number with precision p and scale 0 and is equivalent to NUMBER(p,0).
Specify a floating-point number using the following form:
NUMBER
The absence of precision and scale designators specifies the maximum range and precision for an Oracle number.
And
2
NUMBER[(precision [, scale]])
Number having precision p and scale s. The precision p can range from 1 to 38. The scale s can range from -84 to 127
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Reducing size of datatype involved in index fails where as increasing size work
This question is related to my question in SO Database
events that will cause deletion of index
For example if i create a table like
CREATE TABLE dbo.Customers (ID INT IDENTITY(1,1) PRIMARY KEY CLUSTERED, CustomerName NVARCHAR(200));
CREATE INDEX IX_CustomerName ON dbo.Customers(CustomerName);
And then try to change column datatype like shown below to 230 from 200.
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Msg 5074, Level 16, State 1, Line 1
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Msg 4922, Level 16, State 9, Line 1
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query works successfully. So why does it does not allow reducing the column when index present where as increasing size does not show any problem and works?Hello,
Indeed, a little bit strange even because in BOL it's documented for a different behaviour, see
ALTER TABLE (Transact-SQL) => Remarks =>
"Changing the Size of a Column
You can change the length, precision, or scale of a column by specifying a new size for the column data type in the ALTER COLUMN clause. If data exists in the column, the new size cannot be smaller than the maximum size of the data. Also, the column cannot
be defined in an index, unless the column is a varchar, nvarchar, or varbinary data type and the index is not the result of a PRIMARY KEY constraint. See example P."
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i hav a column phone_no (datatype number) in some database. why it showing the phone no in this format
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What is the size of number data type.
what is the size of number data type (in term of memory storage ;byte ).
Does it make different in size if mention number(38,0)?
Thanks all in advance...:)
Edited by: user10648897 on Jan 7, 2009 6:43 AMNUMBER (p,s)
Number having precision p and scale s. The precision p can range from 1 to 38. The scale s can range from -84 to 127.number(38,0) = number(38)
http://download.oracle.com/docs/cd/B19306_01/server.102/b14196/schema002.htm#sthref472
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