i need to get a percentage but can't use the WHERE clause because it is a part of a large SQL query.
I try to do this :
select (count(sector='Rurality'))/(count(sector))*100 as test from study
But the first count get full results instead of filtering.
In other words, this doesn't work :
select COUNT(sector='Rurality') AS test FROM study;
Maybe somebody could have any idea ? The problem is that filters are glued to the SQL query after all of this but can't add a WHERE sector="rurality".
This is what FILTER is for:
select count(*) filter (where sector = 'Rurality') test from study;
For older PostgreSQL, you can use the CASE construct, but don't forget to omit the ELSE clause to not count NULL values:
select count(case sector when 'Rurality' then 1 end) test from study;
Also, bigint / bigint will be bigint, so use casts and/or parenthesis, or just re-structure your formula, like:
select 100.0 * count(*) filter (where sector = 'Rurality') / count(sector) test
from study;
Your approach works with sum():
select sum((sector='Rurality')::int)::dec / count(sector)*100 as test from study
Use a CASE statement inside the COUNT.
SELECT (COUNT(CASE WHEN sector = 'Rurality' THEN 1 END)) / (COUNT(sector)) * 100 AS test
FROM study
Related
Simplified example:
In hive, I have a table t with two columns:
Name, Value
Bob, 2
Betty, 4
Robb, 3
I want to do a case when that uses the total of the Value column:
Select
Name
, CASE
When value>0.5*sum(value) over () THEN ‘0’
When value>0.9*sum(value) over () THEN ‘1’
ELSE ‘2’
END as var
From table
I don’t like the fact that sum(value) over () is computed twice. Is there a way to compute this only once. Added twist, I want to do this in one query, so without declaring user variables.
I was thinking of scalar queries:
With total as
(Select sum(value) from table)
Select
Name
, CASE
When value>0.5*(select * from total) THEN ‘0’
When value>0.9*(select * from total)THEN ‘1’
ELSE ‘2’
END as var
From table;
But this doesn’t work.
TLDR: Is there a way to simplify the first query without user variables ?
Don't worry about that. Let the optimizer worry about it. But, you can use a subquery or CTE if you don't want to repeat the expression:
select Name,
(case when value > 0.5 * total then '0'
when value > 0.9 * total then '1'
else '2'
end) as var
From (select t.*, sum(value) over () as total
from table t
) t;
Cross join a subquery that fetches the sum to the table:
Select
t.Name
, CASE
When t.value>0.9*tt.value THEN '1'
When t.value>0.5*tt.value THEN '0'
ELSE '2'
END as var
From table t cross join (select sum(value) value from table) tt
and change the order of the WHEN clauses in the CASE expression because as they are, the 2nd case will never succeed.
Since I/O is the major factor the slows down Hive queries, we should strive to reduce the num of stages to get better performance.
So it's better not to use a sub-query or CTE here.
Try this SQL with a global window clause:
select
name,
case
when value > 0.5*sum(value) over w then '0'
when value > 0.9*sum(value) over w then '1'
else '2'
end as var
from my_table
window w as (ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING)
In this case window clause is the recommended way to reduce repetition of code.
Both the windowing and the sum aggregation will be computed only once. You can run explain select..., confirming that only ONE meaningful MR stage will be launched.
Edit:
1. A simple select clause on a subquery is not sth to worry about. It can be pushed down to the last phase of the subquery, so as to avoid additional MR stage.
2. Two identical aggregations residing in the same query block will only be evaluated once. So don’t worry about potential repeated calculation.
I can do this in SQL Server:
SELECT 'HERRAMIENTA ELÉCTRICA' AS TIPO_PRODUCTO,
0 AS DEPRECIACION,
(select sum(empid) from HR.employees) STOCK
but in Access the same query show me the next error:
Query input must contain at least one table or query
So which could be the best form to emulate this? Make a query with any other table looks dirty for me.
EDIT 1:, HR.employees It may no have data, but i want show constants ('HERRAMIENTA ELÉCTRICA',''0') and 0 in the third column, maybe using isnull and this is not the problem here.
Why not to select directly:
select 'HERRAMIENTA ELÉCTRICA' AS TIPO_PRODUCTO,
0 AS DEPRECIACION,
IIF(ISNULL(sum(empid)), 0, sum(empid)) AS STOCK
from HR.employees
This simply doesn't work in Access. You need a FROM clause.
So you need to have a dummy table with one record, even if you don't use a single field from that table.
SELECT 'HERRAMIENTA ELÉCTRICA' AS TIPO_PRODUCTO,
0 AS DEPRECIACION,
(select sum(empid) from HR.employees) STOCK
FROM Dummy_Table
Using this example as empty table:
with employ as
(select 2 as col from dual
minus
select 2 as col from dual)
The query is this one:
select 'HERRAM' as tipo,
0 as deprec,
coalesce(sum(col), 0) as STOCK
from employ;
coalesce(x, value) sets the column to value when X is null
In Access, you can use a system table, and Val and Nz for the zero value:
SELECT TOP 1
'HERRAMIENTA ELÉCTRICA' AS TIPO_PRODUCTO,
0 AS DEPRECIACION,
Val(Nz((select sum(empid) from HR.employees), 0)) AS STOCK
FROM
MSysObjects
I need to calculate the net total of a column-- sounds simple. The problem is that some of the values should be negative, as are marked in a separate column. For example, the table below would yield a result of (4+3-5+2-2 = 2). I've tried doing this with subqueries in the select clause, but it seems unnecessarily complex and difficult to expand when I start adding in analysis for other parts of my table. Any help is much appreciated!
Sign Value
Pos 4
Pos 3
Neg 5
Pos 2
Neg 2
Using a CASE statement should work in most versions of sql:
SELECT SUM( CASE
WHEN t.Sign = 'Pos' THEN t.Value
ELSE t.Value * -1
END
) AS Total
FROM YourTable AS t
Try this:
SELECT SUM(IF(sign = 'Pos', Value, Value * (-1))) as total FROM table
I am adding rows from a single field in a table based on values from another field in the same table using oracle 11g as database and sql developer as user interface.
This works:
SELECT COUNTRY_ID, SUM(
CASE
WHEN ACCOUNT IN 'PTBI' THEN AMOUNT
WHEN ACCOUNT IN 'MLS_ENT' THEN AMOUNT
WHEN ACCOUNT IN 'VAL_ALLOW' THEN AMOUNT
WHEN ACCOUNT IN 'RSC_DEV' THEN AMOUNT * -1
END) AS TI
FROM SAMP_TAX_F4
GROUP BY COUNTRY_ID;
select a= sum(Value) where Sign like 'pos'
select b = sum(Value) where Signe like 'neg'
select total = a-b
this is abit sql-agnostic, since you didnt say which db you are using, but it should be easy to adapat it to any db out there.
I have an SQL statement that counts over the total number of rows active packages whose end date is null. I am currently doing this using (x/y) * 100:
SELECT (SELECT COUNT(*)
FROM packages
WHERE end_dt IS NULL) / (SELECT COUNT(*)
FROM packages) * 100
FROM DUAL;
I wonder if there is a way to make use of any Oracle function to express this more easily?
There's no functionality I'm aware of, but you could simply the query to be:
SELECT SUM(CASE WHEN p.end_dt IS NULL THEN 1 ELSE 0 END) / COUNT(*) * 100
FROM PACKAGES p
So, basically the formula is
COUNT(NULL-valued "end_dt") / COUNT(*) * 100
Now, COUNT(NULL-valued "end_dt") is syntactically wrong, but it can be represented as COUNT(*) - COUNT(end_dt). So, the formula can be like this:
(COUNT(*) - COUNT(end_dt)) / COUNT(*) * 100
If we just simplify it a little, we'll get this:
SELECT (1 - COUNT(end_dt) * 1.0 / COUNT(*)) * 100 AS Percent
FROM packages
The * 1.0 bit converts the integer result of COUNT to a non-integer value so make the division non-integer too.
The above sentence and the corresponding part of the script turned out to be complete rubbish. Unlike some other database servers, Oracle does not perform integer division, even if both operands are integers. This doc page contains no hint of such behaviour of the division operator.
The original post is a little long in the tooth but this should work, using the function "ratio_to_report" that's been available since Oracle 8i:
SELECT
NVL2(END_DT, 'NOT NULL', 'NULL') END_DT,
RATIO_TO_REPORT(COUNT(*)) OVER () AS PCT_TOTAL
FROM
PACKAGES
GROUP BY
NVL2(END_DT, 'NOT NULL', 'NULL');
I'm building a query with a GROUP BY clause that needs the ability to count records based only on a certain condition (e.g. count only records where a certain column value is equal to 1).
SELECT UID,
COUNT(UID) AS TotalRecords,
SUM(ContractDollars) AS ContractDollars,
(COUNTIF(MyColumn, 1) / COUNT(UID) * 100) -- Get the average of all records that are 1
FROM dbo.AD_CurrentView
GROUP BY UID
HAVING SUM(ContractDollars) >= 500000
The COUNTIF() line obviously fails since there is no native SQL function called COUNTIF, but the idea here is to determine the percentage of all rows that have the value '1' for MyColumn.
Any thoughts on how to properly implement this in a MS SQL 2005 environment?
You could use a SUM (not COUNT!) combined with a CASE statement, like this:
SELECT SUM(CASE WHEN myColumn=1 THEN 1 ELSE 0 END)
FROM AD_CurrentView
Note: in my own test NULLs were not an issue, though this can be environment dependent. You could handle nulls such as:
SELECT SUM(CASE WHEN ISNULL(myColumn,0)=1 THEN 1 ELSE 0 END)
FROM AD_CurrentView
I usually do what Josh recommended, but brainstormed and tested a slightly hokey alternative that I felt like sharing.
You can take advantage of the fact that COUNT(ColumnName) doesn't count NULLs, and use something like this:
SELECT COUNT(NULLIF(0, myColumn))
FROM AD_CurrentView
NULLIF - returns NULL if the two passed in values are the same.
Advantage: Expresses your intent to COUNT rows instead of having the SUM() notation.
Disadvantage: Not as clear how it is working ("magic" is usually bad).
I would use this syntax. It achives the same as Josh and Chris's suggestions, but with the advantage it is ANSI complient and not tied to a particular database vendor.
select count(case when myColumn = 1 then 1 else null end)
from AD_CurrentView
How about
SELECT id, COUNT(IF status=42 THEN 1 ENDIF) AS cnt
FROM table
GROUP BY table
Shorter than CASE :)
Works because COUNT() doesn't count null values, and IF/CASE return null when condition is not met and there is no ELSE.
I think it's better than using SUM().
Adding on to Josh's answer,
SELECT COUNT(CASE WHEN myColumn=1 THEN AD_CurrentView.PrimaryKeyColumn ELSE NULL END)
FROM AD_CurrentView
Worked well for me (in SQL Server 2012) without changing the 'count' to a 'sum' and the same logic is portable to other 'conditional aggregates'. E.g., summing based on a condition:
SELECT SUM(CASE WHEN myColumn=1 THEN AD_CurrentView.NumberColumn ELSE 0 END)
FROM AD_CurrentView
It's 2022 and latest SQL Server still doesn't have COUNTIF (along with regex!). Here's what I use:
-- Count if MyColumn = 42
SELECT SUM(IIF(MyColumn = 42, 1, 0))
FROM MyTable
IIF is a shortcut for CASE WHEN MyColumn = 42 THEN 1 ELSE 0 END.
Not product-specific, but the SQL standard provides
SELECT COUNT() FILTER WHERE <condition-1>,
COUNT() FILTER WHERE <condition-2>, ...
FROM ...
for this purpose. Or something that closely resembles it, I don't know off the top of my hat.
And of course vendors will prefer to stick with their proprietary solutions.
Why not like this?
SELECT count(1)
FROM AD_CurrentView
WHERE myColumn=1
I had to use COUNTIF() in my case as part of my SELECT columns AND to mimic a % of the number of times each item appeared in my results.
So I used this...
SELECT COL1, COL2, ... ETC
(1 / SELECT a.vcount
FROM (SELECT vm2.visit_id, count(*) AS vcount
FROM dbo.visitmanifests AS vm2
WHERE vm2.inactive = 0 AND vm2.visit_id = vm.Visit_ID
GROUP BY vm2.visit_id) AS a)) AS [No of Visits],
COL xyz
FROM etc etc
Of course you will need to format the result according to your display requirements.
SELECT COALESCE(IF(myColumn = 1,COUNT(DISTINCT NumberColumn),NULL),0) column1,
COALESCE(CASE WHEN myColumn = 1 THEN COUNT(DISTINCT NumberColumn) ELSE NULL END,0) AS column2
FROM AD_CurrentView