How to select on table and count occurrences some values

问题

I am asking you for a help because I do not know SQL very well.

I need to count occurrences some values from table column to achieve effect like statistics table which will look like at the picture below:

Needed result:

Comment:

My Result Table needs to have first two columns (contry and site) comes from first table "Violations" and next 5 columns which will contain numbers (count) of occurrences status_id in "Violations" in each of possible values of id from Status table.

Explanation:

So, I have existing two tables: Violations and Status. Please look at my sqlfiddle

Violations:

id long,
country varchar(20),
site varchar(20),
status_id long, <-- this is the id of status in Status table.
... other columns not important in this case

Status:

id long,
status long Column "status" have values (1-4) which are mapped to string values: Suspected Violation (1), Confirmed Violation (2), Confirmed No Violation (3), Not Determined (4)

In result of my join (or based only on one table Violations) is to have table which should contain columns:

from Violations table: "Country" and "Site"
from Status table: "Suspected Violation", "Confirmed Violation", "Confirmed No Violation", "Not Determined", "Total" (where this columns are counters of occurrences in Violation table).

Current Status and new Requirements:

First try is done (thanks to bluefeet) below and is almost perfect...

select v.country,
v.site,
    SUM(case when s.id = 1 then 1 else 0 end) Total_SuspectedViolations,
    SUM(case when s.id = 2 then 1 else 0 end) Total_ConfirmedViolations,
    SUM(case when s.id = 3 then 1 else 0 end) Total_ConfirmedNoViolations,
    SUM(case when s.id = 4 then 1 else 0 end) Total_NotDetermined,
    COUNT(*) Total
from violations v
inner join status s
    on v.status_id = s.id
group by v.country, v.site

or without JOIN:

select v.country,
v.site,
    SUM(case when v.status_id = 1 then 1 else 0 end) Total_SuspectedViolations,
    SUM(case when v.status_id = 2 then 1 else 0 end) Total_ConfirmedViolations,
    SUM(case when v.status_id = 3 then 1 else 0 end) Total_ConfirmedNoViolations,
    SUM(case when v.status_id = 4 then 1 else 0 end) Total_NotDetermined,
    COUNT(*) Total
from violations v
group by v.country, v.site

...but is not including 3 issues as you can see in the picture which should be. I mean:

"- All -" which should count occurrences for all countries
"- Unknown -" which should count occurrences for some not recognized countries
"- All -" (regarding to each country) - which should count occurrences within one country

Additional Explanation:

-Unknown- meaning:

Unknown should count occurrences for countries which for example do not exists in DB Country table or have a wrong name/id and that's why is treated here as Unknown (I forgot mention that there is table Country in DB). The same for sites, Unknown for sites means that someone put wrong value in Violations.status_id not from range (1-4) because these are only acceptable values existing in Status table.

We can assume that table Country looks like:

Country:

id long,
name varchar(30)

Please help me to write correct sql query which would include these 3 conditions, because I have a big problem to do that.

回答1:

The All case can be easily done using UNION statement (see sqlFiddle for results):

(SELECT v.country,
    v.site,
    SUM(CASE WHEN v.status_id = 1 THEN 1 ELSE 0 END) Total_SuspectedViolations,
    SUM(CASE WHEN v.status_id = 2 THEN 1 ELSE 0 END) Total_ConfirmedViolations,
    SUM(CASE WHEN v.status_id = 3 THEN 1 ELSE 0 END) Total_ConfirmedNoViolations,
    SUM(CASE WHEN v.status_id = 4 THEN 1 ELSE 0 END) Total_NotDetermined,
    COUNT(*) Total,
    0  'isAll'
FROM violations v
GROUP BY v.country, v.site)
union(
SELECT v.country,
    '- All -',
    SUM(CASE WHEN v.status_id = 1 THEN 1 ELSE 0 END) Total_SuspectedViolations,
    SUM(CASE WHEN v.status_id = 2 THEN 1 ELSE 0 END) Total_ConfirmedViolations,
    SUM(CASE WHEN v.status_id = 3 THEN 1 ELSE 0 END) Total_ConfirmedNoViolations,
    SUM(CASE WHEN v.status_id = 4 THEN 1 ELSE 0 END) Total_NotDetermined,
    COUNT(*) Total,
  1  'isAll'
FROM violations v
GROUP BY v.country)
UNION (
SELECT '- All -',
    '- All -',
    SUM(CASE WHEN v.status_id = 1 THEN 1 ELSE 0 END) Total_SuspectedViolations,
    SUM(CASE WHEN v.status_id = 2 THEN 1 ELSE 0 END) Total_ConfirmedViolations,
    SUM(CASE WHEN v.status_id = 3 THEN 1 ELSE 0 END) Total_ConfirmedNoViolations,
    SUM(CASE WHEN v.status_id = 4 THEN 1 ELSE 0 END) Total_NotDetermined,
    COUNT(*) Total,
  1  'isAll'
FROM violations v)
ORDER BY country, isAll DESC, site

However, the performance may not be really great with that kind of query, so I'm not saying it's the best possible solution - but it works.

Version with 'Unknow'

http://www.sqlfiddle.com/#!2/abfb7/21

(SELECT IF(c.name IS NULL, '- Unknow -', c.name) as name,
    v.site,
    SUM(CASE WHEN v.status_id = 1 THEN 1 ELSE 0 END) Total_SuspectedViolations,
    SUM(CASE WHEN v.status_id = 2 THEN 1 ELSE 0 END) Total_ConfirmedViolations,
    SUM(CASE WHEN v.status_id = 3 THEN 1 ELSE 0 END) Total_ConfirmedNoViolations,
    SUM(CASE WHEN v.status_id = 4 THEN 1 ELSE 0 END) Total_NotDetermined,
    COUNT(*) Total,
    0  'isAll'
FROM violations v LEFT JOIN country c ON c.name = v.country
GROUP BY c.name, v.site)
union(
SELECT IF(c.name IS NULL, '- Unknow -', c.name) as name,
    '- All -',
    SUM(CASE WHEN v.status_id = 1 THEN 1 ELSE 0 END) Total_SuspectedViolations,
    SUM(CASE WHEN v.status_id = 2 THEN 1 ELSE 0 END) Total_ConfirmedViolations,
    SUM(CASE WHEN v.status_id = 3 THEN 1 ELSE 0 END) Total_ConfirmedNoViolations,
    SUM(CASE WHEN v.status_id = 4 THEN 1 ELSE 0 END) Total_NotDetermined,
    COUNT(*) Total,
  1  'isAll'
FROM violations v LEFT JOIN country c ON c.name = v.country
GROUP BY c.name)
UNION (
SELECT '- All -',
    '- All -',
    SUM(CASE WHEN v.status_id = 1 THEN 1 ELSE 0 END) Total_SuspectedViolations,
    SUM(CASE WHEN v.status_id = 2 THEN 1 ELSE 0 END) Total_ConfirmedViolations,
    SUM(CASE WHEN v.status_id = 3 THEN 1 ELSE 0 END) Total_ConfirmedNoViolations,
    SUM(CASE WHEN v.status_id = 4 THEN 1 ELSE 0 END) Total_NotDetermined,
    COUNT(*) Total,
  1  'isAll'
FROM violations v LEFT JOIN country c ON c.name = v.country)
ORDER BY name, isAll DESC, site

回答2:

Using with rollup you will get the needed sum field which you want

select v.country,
v.site,
SUM(case when s.id = 1 then 1 else 0 end) Total_SuspectedViolations,
SUM(case when s.id = 2 then 1 else 0 end) Total_ConfirmedViolations,
SUM(case when s.id = 3 then 1 else 0 end) Total_ConfirmedNoViolations,
SUM(case when s.id = 4 then 1 else 0 end) Total_NotDetermined,
COUNT(*) Total
from violations v
     inner join status s
     on v.status_id = s.id
group by v.country, v.site WITH ROLLUP

Hope this helps

REFER for with rollup documentation

FIDDLE

来源：https://stackoverflow.com/questions/15360976/how-to-select-on-table-and-count-occurrences-some-values

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sql