I have a query that shows percentage of a job being to completion. Here is my query:
NVL(substr(countprocess_locations.count_attempt_id)/count(processes.process_id),2,2),0)||'%' as "Percentage Complete"
Everything has worked fine and beautifully, BUT I recently had a count hit 100% mathematically, but in the output of the query it says 0. I've tried playing with 2,2),0 and no difference so far :/
Any help would be greatly appreciated.
Sample
With a working example breaking it down.
159 / 180 = 0.883333
SUBSTR first converts it to text, when doing so Oracle drops the leading zero
.883333
SUBSTR then takes two characters starting at the second
.*88*3333
Then you concatenate '%' to it
88%
When you have 100% it flows such:
2000 / 2000 = 1
Converts to text
1
Takes two characters starting at the second
NULL
Then your NVL returns 0.
Instead of SUBSTR you should * 100 and then ROUND or if you really want to just drop the digits instead of rounding use TRUNC.
NVL(ROUND((countprocess_locations.count_attempt_id)/count(processes.process_id))*100,0),0)||'%'
Related
SQL Server decimal function not working as intended.
To test with sample data, I created a table and inserted values to it.
Then, I tried to run decimal function on these values.
CREATE TABLE TEST_VAL
(
VAL float
)
SELECT * FROM TEST_VAL
Output:
VAL
----------
16704.405
20382.135
2683.135
SELECT CAST(VAL AS DECIMAL(15, 2)) AS NEWVAL
FROM TEST_VAL;
Output:
NEWVAL
-------------
16704.40
20382.13
2683.14
I expected same formatting for all 3 values. But, for third value it returns ceiling round off value.
This is due to the nature of floating point numbers being inexact and being in binary. But I want to demonstrate how this is working.
The issue is that a decimal such as 0.135 cannot be represented exactly. As the floating point representation, it would typically be something like:
0.134999999234243423
(Note that these numbers as with all representations of values in this answer are made up. They are intended to be representative to make the point.)
The number of 9s is actually larger. And the subsequent digits are just representative. In this representation, we wouldn't see a problem with truncating the value. After all 0.1349999 should round to the same value as 0.13499.
In binary, this looks different:
0.11101000010101 10011 10011 10011 10011 . . .
---------------- --------------
~0.135 "arbitrary" repeating pattern
(Note: The values are made up!)
That is, the "infinite" portion of binary representation is not a bunch of repeating 1s or repeating 0s; it has a pattern. This is analogous the inverse of most numbers in base 10 For instance, 1/7 has a repeating component of six digits, 142857. We tend to forget this, because common inverses are either exact (1/5 = 0.2) or have a single repeating digit (1/6 = 0.166666...). 1/7 is the first case that is not so simple -- and almost all decimals are like this. For rational numbers, there is always a repeating sequence regardless of base and it is never longer than dividend (number at the bottom) minus 1).
We can think of this as all decimal representations (regardless of base) always have some number of digits that are repeating. For an exact representation, the repeating portion is 0. For others it is rarely one digit. Usually, it is multiple digits. And it is a fun exercise in mathematics to characterize this. But all that is important is that the repeating portion has 1s and 0s.
Now, what is happening. A floating point number has three parts:
a magnitude. This is a number of bits that represent the exponent.
an integer portion, which is the number before the decimal point.
an integer portion, which is the number after the decimal point.
(Actually, the last two are really one integer, but I find it much easier to explain this by splitting them into two components.)
Only a fixed number of bits are available for the two integer portions. What does this look like? Once again the representative patterns are something like this:
0.135 0 11101000010101100111001110
1.135 1 11101000010101100111001110
2.135 10 1110100001010110011100111
4.135 100 111010000101011001110011
8.135 1000 11101000010101100111001
16.136 10000 1110100001010110011100
-----------^ part before the decimal
------------------^ part after the decimal
Note: This is leaving off the magnitude portion of the decimal representation.
As you can see, digits get chopped off from the end. But sometimes it is 0 that gets chopped off -- so there is no change in the value being represented. And sometimes it is a 1. And there is a change.
With this, you might be able to see how the values essentially fluctuate, say:
0.135 --> 0.135000000004
1.135 --> 0.135000000004
2.135 --> 0.135000000004
4.135 --> 0.135000000001
8.135 --> 0.135999999997
16.135 --> 0.135999999994
These are then rounded differently, which is what you are seeing.
I put together this little db<>fiddle, so you can see how the rounding changes around powers of two.
Perhaps this could be explained if we extend the precision of the three numbers in the first query:
16704.4050
20382.1349
2683.1351
Rounding each of the above to only two decimal places, which is what a cast to DECIMAL(10,2) would do, would yield:
16704.40
20382.13
2683.14
Would this be of use:
select CONVERT(DECIMAL(15,2), ROUND(VAL, 2, 1)) AS NEWVAL
from TEST_VAL;
Here is the DEMO for SQLServer 2012 : DEMO
first question : why they are not same value?
because their type is different , CAST(VAL as decimal(4,2)) will format like ##.## not ##.### so in your case it get ceiling round value.
Why not use the same type ?
CREATE TABLE T
(
[VAL] DECIMAL(8,3)
);
INSERT INTO T ([VAL])
VALUES (16704.405), (20382.135), (2683.135);
SELECT * FROM T
Output:
VAL
-----------
16704.405
20382.135
2683.135
db<>fiddle here
or you can cast AS DECIMAL(8, 3)
SELECT CAST(VAL AS DECIMAL(8,3)) AS NEWVAL
FROM T;
I need to round off couple of fields that I extract from Teradata SQL assistant.
Currently I am using CAST(Field1 as numeric(20,2)) as Field1
18.529 is rounded to 18.53 but 36.425 is rounded to 36.42 instead I am expecting 36.43
How can this be achieved?
The rounding rules for CASTs depend on a global setting, RoundHalfwayMagUp in dbscontrol.
You might try the ROUND function which defaults to the rounding rules you prefer:
ROUND(36.425,2)
I found an old post on a forum here which states that the RoundHalfwayMagUp controls whether .5 rounds up or down. See the docs for more info
because in 36.425, 5 is near to 0 not to 10,
if you put 36.426 it will round of to 36.43
Round :
It will work like below
between 0 and 5 > increment by 0( replaced )
between 5 to 10 > increment by 1 ( replaced)
I have two database fields that require significant precision - one column is decimal(36,12) and another is decimal(36,24).
When multiplying them I was expecting that precision will be preserved, however that seems not to be the case - I actually get less precision. For example when running following SQL:
SELECT 3.035 * 0.333333333333333333333333 AS Normal
SELECT CAST(3.035 AS DECIMAL(36,12)) * CAST(0.333333333333333333333333 AS DECIMAL(36,24)) AS Cast12
SELECT CAST(3.035 AS DECIMAL(36,24)) * CAST(0.333333333333333333333333 AS DECIMAL(36,24)) AS Cast24
I get following results:
Normal : 1.011666666666666666666665655
Cast12 : 1.011667
Cast24 : 1.0116666666667
I guess this is because multiplication is operation that usually yields "bigger" number. I obviously can find a way around this (Cast24 is "good enough"), but I want to understand how exactly does SQL Server determines when to round and what digits to keep?
The combination of the following articles should answer your question.
http://cuisinecode.blogspot.com/2014/04/losing-precision-after-multiplication.html
http://technet.microsoft.com/en-us/library/ms190476.aspx
I am querying to find things ending in "ST" followed by a number 1 - 999.
SELECT NUMBER WHERE NUMBER LIKE '%ST -- works correctly to return everything ending in "ST"
SELECT NUMBER WHERE NUMBER LIKE '%[1-999] -- works correctly to return everything ending in 1 - 999
SELECT NUMBER WHERE NUMBER LIKE '%ST[1-999] -- doesn't work - returns nothing
Also tried:
SELECT NUMBER WHERE NUMBER LIKE '%ST%[1-999] -- works, but also returns things like "GRASTNT3" that have extra things between the "ST" and the number
Can anyone help this struggling beginner?
Thanks!
The problem is that [1-999] doesn't mean what you think it does.
SQL Server interprets that as a set of values (1-9, 9, 9) which basically means that if there's more than 1 digit after the ST, the entry won't be returned.
So far as I can tell, your best bet is:
SELECT NUMBER WHERE
NUMBER LIKE '%ST[1-9][0-9][0-9]' OR
NUMBER LIKE '%ST[1-9][0-9]' OR
NUMBER LIKE '%ST[1-9]'
(assuming that your numbers don't have leading zeros - if they do, replace the ones with more zeros)
You need to do
SELECT NUMBER WHERE
NUMBER LIKE '%ST[1-9][0-9][0-9]'
OR NUMBER LIKE '%ST[1-9][0-9]'
OR NUMBER LIKE '%ST[1-9]';
The group in the the [] is a Char/NChar not an Int.
Better still normalise and type your data, so you have an ST bit and an int column for the number.
If you find you need to define different filters on variable string data, consider Full Text Searching or another Lucene related technology depending on your RDBMS.
What if somebody made a column as VARCHAR2(256 CHAR) and there are only numbers in this column. I would like to get the highest number. The problem is: the number is something > 999999 but a Max to a varchar is always giving me a max number of 999999
I tried to_number(max(numbers), '9999999999999') but i still get 999999 back, at that cant be. Any ideas? Thank you
the best way is to
First Solution
convert the column in numeric
or
Second Solution
convert data in you query in numeric and than get data...
Example
select max(col1) from(
select to_number(numbers) as col1 from table ) d
It has to be this way because if you call MAX() before TO_NUMBER(), it will sort alphabetically, and then 999999 is bigger than 100000000000. Note that applying TO_NUMBER() to a varchar2 column incurs the risk of an INVALID_NUMBER exception, should the column containing any non-numeric characters. This is why the first proposed solution is to be preferred.
In Oracle, the NUMBER type contains base 100 floating point values which have a precision of 38 significant digits, and a max value of 9999...(38 9's) x 10^125. There are two questions at issue - the first is whether a NUMBER can contain a value converted from a 256 character string, and the second is if two such values which are 'close' in numeric terms can be distinguished.
Let's start with taking a 256 character string and trying to convert it to a number. The obvious thing to do is:
SELECT TO_NUMBER('9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999') AS VAL
FROM DUAL;
Executing the above we get:
ORA-01426: numeric overflow
which, having paid attention earlier, we expected. The largest exponent that a NUMBER can handle is 125 - and here we're trying to convert a value with 256 significant digits. NUMBER's can't handle this. If we cut the number of digits down to 125, as follows:
SELECT TO_NUMBER('99999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999') AS VAL
FROM DUAL;
It works fine, and our answer it 1E125.
<blink>
WHOA! WAIT!! WHAT??? The answer is 1 x 10^125??? What about all those 9's?!?!?!?
Remember earlier I'd mentioned that an Oracle NUMBER is a floating point value with a maximum precision of 38 and a maximum exponent of 125. From the point of view of TO_NUMBER 125 9's all strung together can't be exactly represented - too many digits (remember, max. precision of 38 (more on this later)). So it does the absolute best it can - it converts the first 38 digits (all of which are 9's) and then says "How should I best round this off to make the result A) representative of the input and B) as close as I can get to what I was given?". In this case it looks at digit 39, sees that it's a 9, and decides to round upward. As all the other digits are also 9's, it continues rounding neatly until it ends up with 1 as the remaining mantissa digit.
* Later, back at the ranch... *
OK, earlier I'd mentioned that NUMBER has a precision of 38 digits. That's not entirely true - it can actually differentiate between values with up to 40 digits of precision, at least sometimes, if the wind is right, and you're going downhill. Here's an example:
SELECT CASE
WHEN to_number('9999999999999999999999999999999999999999') >
to_number('9999999999999999999999999999999999999998')
THEN 'Greater'
ELSE 'Not greater'
END AS VAL
FROM DUAL;
Those two values each have 40 digits (counting is left as an exercise to the extremely bored reader :-). If you execute the above you'll get back 'Greater', showing that the comparison of two 40 digit values succeeded.
Now for some fun. If you add an additional '9' to each string, making for a 41 digit value, and re-execute the statement it'll return 'Not greater'.
<blink>
WAIT! WHAT?? WHOA!!! Those values are obviously different! Even a TotalFool (tm) can see that!!
The problem here is that a 41 digit number exceeds the precision of the NUMBER type, and thus when TO_NUMBER finds it has a value this long it starts discarding digits on the right side. Thus, even though those two really big numbers are clearly different to you and me, they're not different at all once they've been folded, spindled, mutilated, and converted.
So, what are the takeaways here?
1 - To the OP's original question - you'll have to come up with another way to compare your number strings besides using NUMBER because Oracle's NUMBER type can't hold 256 digit values. I suggest that you normalize the strings by making sure ALL the values are 256 digits long, adding zeroes on the left as needed, and then a string comparison should work OK.
2 - Floating point numbers prove the existence of (your favorite deity/deities here) by negation, as they are clearly the work of (your favorite personification of evil here). Whenever you work with them (as we all have to, sooner or later) you should remember that they are the foul byproducts of malignant evil, waiting to lash out at you when you least expect it.
3 - There is NO point three! (And extra credit for those who can identify without resorting to an extra-cranial search engine where this comes from :-)
Share and enjoy.
If you mean that the numbers in the column can be that big (256 digits), you could try something like this:
SELECT numbers
FROM (
SELECT numbers
FROM table_name
ORDER BY LPAD(numbers, 256) DESC
)
WHERE rownum = 1
or like this:
SELECT LTRIM(MAX(LPAD(numbers, 256))) AS numbers
FROM table_name