Given two numeric properties n.in and n.out, how can I get the sum of them?
My query
match (n)
return n.name, id(n), sum(n.in,n.out);
But obviously this is false since SUM is for only one property. Looking at Numeric mathematical functions there is no such function too.
Like this?
match(n)
with sum(n.in + n.out) as sumOfAllNodes
match(n)
return n.name, id(n), n.in + n.out as sumOfaNode, sumOfAllNodes
Related
How can I enter multiple values into an aggregate function using just data I enter at the command line? Say, in Postgres, I run the following.
SELECT AVG(2);
I'll get the correct answer, but I can't find a way to enter multiple values, such as below, without getting an error.
SELECT AVG(1,NULL,2,3);
I've tried wrapping the numbers in various brackets but to no effect. What's the syntax I'm missing?
EDIT: Additionally, is there a way to include NULLs in the input?
AVG() is an aggregate that operates over multiple rows. So you need to convert your comma separated list to one row per value to be able to use an aggregate like avg(). This could be done using e.g. string_to_table
select avg(num::numeric)
from string_to_table('1,2,3', ',') as x(num)
If you want to include a NULL value, you could add it to the list and convert it to null before casting it to a numeric value:
select avg(nullif(num, 'null')::numeric)
from string_to_table('1,2,3,4,null', ',') as x(num)
Actually I'm a bit confused about what should i wrote in the subject.
The point is like this, I want to average the Speed01,Speed02,Speed03 and Speed04 :
SELECT
Table01.Test_No,
Table01.Speed01,
Table01.Speed02,
Table01.Speed03,
Table01.Speed04,
I want to create new column that consists of this average -->>
AVG(Table01.Speed01, Table01.Speed02, Table01.Speed03,Table01.Speed04) as "Average"
I have tried this, but it did not work.
From
Table01
So, the contain of the Speed column could be exist but sometimes the Speed02 don't have number but the others are have numbers. sometimes speed04 data is also missing and the others is exist, sometimes only one data (example: only Speed01) have the data. lets say it depends on the sensor ability to catch the speed of the test material.
It will be a big help if you can find the solution. I'm newbie here.
THANK YOU ^^
AVG is a SQL aggregate function, therefore not applicable. So simply do the math. Average is sum divided by count:
(SPEED01 + SPEED02 + SPEED03 +SPEED04)/4
To deal with missing values, use NULLIF or COALESCE:
(COALESCE(SPEED01, 0) + COALESCE(SPEED02, 0) + COALESCE(SPEED03, 0) + COALESCE(SPEED04, 0))
That leaves the denominator. You need to add 1 for every non null. For example:
(COALESCE(SPEED01/SPEED01,0) + COALESCE(SPEED02/SPEED02,0) + ...)
You can also use CASE, depending on the supported SQL dialect, to avoid the possible divide by 0:
CASE WHEN SPEED01 IS NULL THEN 0 ELSE 1
OR you can normalize the data, extract all SPEEDs into a 1:M relation and use the AVG aggregate, avoiding all these issues. Not to mention the possibility to add a 5th measurement, then a 6th and so on and so forth!
Just add the columns and divide them by 4. To deal with the "missing" values use coalesce to treat NULL values as zero:
SELECT Test_No,
(coalesce(Speed01,0) + coalesce(Speed02,0) + coalesce(Speed03,0) + coalesce(Speed04,0)) / 4 as "Average"
FROM Table01;
You didn't mention your DBMS (Postgres, Oracle, ...), but the above is ANSI (standard) SQL and should run on nearly every DBMS.
As I understood your question, I supposed that Table01.Speed01, Table01.Speed03, Table01.Speed04 are nullable and of type int whereas Table01.Speed02 is nullable and of type nvarchar:
SELECT
Table01.Test_No,
(
ISNULL(Table01.Speed01, 0) +
CASE ISNUMERIC(Table01.Speed02) WHEN 0 THEN 0 ELSE CAST(Table01.Speed02 AS int) END +
ISNULL(Table01.Speed03, 0) +
ISNULL(Table01.Speed04, 0)
)/4 AS AVG
FROM Table01
I want to perform comparison for the specified columns in database, the comparison logic should compare the numbers regardless of their signs and will retrieve the result original with its sign.
For example, below code works well but as can be seen in the select block it returns the absolute value of columns. Is there any trick, cheat in Firebird 2.1 to overcome that?
SELECT a.ELM_NUM,a.COMBO, maxvalue(abs(a.N_1),abs(a.N_2)) as maxN from ntm a order by a.ELM_NUM
You can use a CASE condition:
SELECT a.ELM_NUM,a.COMBO,
CASE WHEN abs(a.N_1) > abs(a.N_2) THEN a.N_1 ELSE a.N_2 END as maxN
from ntm a
order by a.ELM_NUM
I have 2 questions regarding array_agg in postgres
1) I have a column which is of type array_agg. I need to divide each of the element of the array_agg by a constant value. Is it possible. I checked http://www.postgresql.org/docs/9.1/static/functions-array.html, but could not find any reference to any arithmetic operations on array_agg.
Edit:
An example of the desired operation.
select array_agg(value)/2 from some_table
Here, I create an array of the column value from the table some_table and I have to divide each of the column by 4
2) Is it possible to use coalesce in array_agg. In my scenario, there may be cases wherein, the array_agg of a column may result in a NULL array. Can we use coalesce for array_agg ?
Example:
select coalsece(array_agg(value1), 0)
Dividing is probably simper than you thought:
SELECT array_agg(value/2)
FROM ...
However, what value/2 does exactly depends on the data type. If value is an integer, fractional digits are truncated. To preserve fractional digits use value/2.0 instead. The fractional digit forces the calculation to be done with numeric values.
COALESCE won't make any difference outside the array. Either there are no rows, then you get no result at all ('no row'), or if there are, you get an array, possibly with NULL elements. But the value of the array itself is never NULL.
To replace individual NULL values with 0:
SELECT array_agg(coalesce(value/2.0, 0))
FROM ...
How to find the maximum of two explicit values in MySQL? Something like MAXIMUM(1, #foo).
There are group functions like MAX, MIN, AVG, etc that take column name as an argument and work with result sets. Is it possible to convert two explicit values to a result set and use those functions? Some other ways?
P.S.: I need a max function for one of my stored procedures.
How to find the maximum of two explicit values in MySQL? Something like MAXIMUM(1, #foo).
Use the GREATEST function:
GREATEST(1, #foo)
...will return whichever value is larger - if 1 is larger than the value in #foo, you'll get 1. Otherwise, you'll get whatever value is in #foo. Also, it's not an aggregate function.
The alternative would be to use a CASE statement:
CASE WHEN 1 > #foo THEN 1 ELSE #foo END
...because CASE is ANSI standard - that will work on Oracle, MySQL, SQL Server, Postgres...
You can use IF(1 > #foo,1,#foo)