Let's say I have a table with 2 columns - A & B.
Using plain SQL (No scripts/cursors etc.), how do I (window function?) calculate for EACH value in column A the number of values in column B that are bigger/smaller than it?
Thanks you.
You would use conditional aggregation:
select a,
sum(case when b < a then 1 else 0 end)
from t
group by a;
Window functions don't seem appropriate to this question.
Related
Ok so this gets me the count of how many Records of type A are blank in column B
SELECT A, Count(B)
FROM `table1`
where
B = ""
group by A
it gives me a table
A
B
First
564
Second
1985
And that is great. But I want this to summarize by counting blanks in multiple columns, not just blanks in column B, like this:
A
B
C
First
564
9001
Second
1985
223
I have an intuition that this is done by creating another table first that would look like this
A
Column
Value
First
"B"
B value
First
"C"
C value
Second
"B"
B value
Second
"C"
C value
for every document, so you can count blanks, but I'm not sure how to get there. Is this the right approach? or is there a much simpler version using pivot tables or similar?
You could try using a conditional sum,
select A,
Sum(case when b='' then 1 end) B,
Sum(case when c='' then 1 end) C
from t
group by A
I'm using SQL Server 14 and I need to count the number of null values in a row to create a new column where a "% of completeness" for each row will be stored. For example, if 9 out of 10 columns contain values for a given row, the % for that row would be 90%.
I know this can be done via a number of Case expressions, but the thing is, this data will be used for a live dashboard and won't be under my supervision after completion.
I would like for this % to be calculated every time a function (or procedure? not sure what is used in this case) is run and need to know the number of columns that exist in my table in order to count the null values in a row and then divide by the number of columns to find the "% of completeness".
Any help is greatly appreciated!
Thank you
One method uses cross apply to unpivot the columns to rows and count the ratio of non-null values.
Assuming that your table has columns col1 to col4, you would write this as:
select t.*, x.*
from mytable t
cross apply (
select avg(case when col is not null then 1.0 else 0 end) completeness_ratio
from (values (col1), (col2), (col3), (col4)) x(col)
) x
I need some advice in google query language.
I want to count rows depending on date and a condition. But if the condition is not met, it should return 0.
What I'm trying to achieve:
Date Starts
05.09.2018 0
06.09.2018 3
07.09.2018 0
What I get:
Date Starts
06.09.2018 3
The query looks like =Query(Test!$A2:P; "select P, count(B) where (B contains 'starts') group by P label count(B) 'Starts'")
P contains ascending datevalues and B an event (like start in this case).
How can I force output a 0 for the dates with no entry containing "start"?
The main point is to get all needed data in one table in ascending order. But this is only working, if every day has an entry. If there is no entry for a day, the results for "start" do not match the datevalue in column A. 3 in column D would be in the first row of the table then.
I need it like this:
A B C D
Date Logins Sessions Starts
05.09.2018 1 2 0
06.09.2018 3 4 3
07.09.2018 4 5 0
Maybe this is easy to fix, but I don't see it.
Thanks in advance!
You can do some pre-processing before the query. Ex: check if column B contains 'start' with regexmatch and use a double unary (--) to force the boolean values into 1's and 0's. The use query to sum.
=Query(Arrayformula({--regexmatch(Test!$B2:B; "start")\ Test!$A2:P}); "select Col17, sum(Col1) where Col17 is not null group by Col17 label sum(Col1) 'Starts'")
Change ranges to suit.
just a simple question but somehow I can't find an answer here.
I have two columns (A and B). Both contains numbers with zeros and null. I would like to get a division one by the other to get information about the ratio between each single row but I am getting ORA-01476.
I know the divisior is equal to zero but I would like to get in this row a number and not an error for whole query
A B
1 5
2 Null
3 0
NULL 3
0 4
4
I am using sql developer.
If you divide a number by zero you get an error, because the answer to such division is undefined. SQL, however, has a value for undefined: NULL. So make the result NULLinstead:
select a, b, case when b = 0 then null else a / b end as ratio
from mytable;
or
select a, b, a / case when b = 0 then null else b end as ratio
from mytable;
This is standard SQL and works in Oracle as well as in about every other RDBMS. Oracle also provides the function NULLIF as a shorter way to write the expression in the second query.
You can use nullif to return null instead of raising an error:
select A / nullif(B, 0) as division
from YourTable
If your numbers are stored as varchar, cast them to numbers before using them:
select to_number(A) / nullif(to_number(B), 0) as division
from YourTable
i guess i just lack the keywords to search, but this is burning on my mind:
how can i add a condition to the sum-function in the select-statement like
select sum(a), sum(b where c=1) from db;?
this means, i want to see the sum of column a and the sum of column b, but only of the records in column b of which column c has the value 1.
the output of heidi just says "bad syntac near WHERE". may there be any other way?
thanks in advance and best regards from Berlin, joachim
The exact syntax may differ depending on the database engine, however it will be along the lines of
SELECT
sum(a),
sum(CASE WHEN c = 1 THEN b ELSE 0 END)
FROM
db
select sum(case when c=1 then b else 0 end)
This technique is useful when you need a lot of aggregates on the same set of data - you can query the entire table without applying a where filter, and have a bunch of these which give you aggregated data for a specific filter.
It's also useful when you need a lot of counts based on filters - you can do sums of 1 or 0:
select sum(case when {somecondition} then 1 else 0 end)