I have 2 table member_asrama and asrama. I want count row row_asrama with condition, but the result not showing result 0 from count.
Table member_asrama:
id asrama_id period_id
1 1 1
Table asrama
id name
1 A
2 B
My query
SELECT asrama.id,asrama.name, COUNT(*) as cnt
FROM asrama
left join member_asrama
on asrama.id = member_asrama.`asrama_id`
where member_asrama.`period_id` = 1
group by asrama.id
Result
asrama.id asrama.name cnt
1 A 1
I want result
asrama.id asrama.name cnt
1 A 1
2 B 0
Basically, the condition needs to be in the ON clause:
select a.id, a.name, count(ma.asrama_id) as cnt
from asrama a left join
member_asrama ma
on a.id = ma.asrama_id and
ma.period_id = 1
group by a.id, a.name;
Note other changes:
COUNT() counts a column from member_asrama. That allows 0 in the results.
Table aliases make the query easier to write and to read.
Backticks make the query harder to write and read -- and they are not necessary.
I included both columns in the GROUP BY. Technically, this is not necessary if id is a primary/unique key. However, it is a good habit if you are learning SQL.
Related
I have two MySQL tables A and B both with this schema
ID
entity_id
asset
asset_type
0
12345
x
1
..
.........
.....
..........
I would like to get an aggregated top 10/50/whatever entity_ids with the largest row count difference between the two tables. I think I could do this manually by just getting the highest row count by entity_id like so
select count(*), entity_id
-> from A
-> group by entity_id
-> order by count(*) desc;
and just manually comparing to the same query for table B but I'm wondering if there's a way to do this in just one query, that compares row counts for each distinct entity_id and aggregates the differences between row counts. A few notes
There is an index on entity_id for both tables
Table B will always have an equivalent or greater number of rows for each entity_id
Sample output
entity_id
difference
12345
100
3232
75
5992
40
and so on
for top 10/50
Aggregate in each table and join the results to get the difference:
SELECT a.entity_id, b.counter - a.counter diff
FROM (SELECT entity_id, COUNT(*) counter FROM A GROUP BY entity_id) a
INNER JOIN (SELECT entity_id, COUNT(*) counter FROM B GROUP BY entity_id) b
ON a.entity_id = b.entity_id
ORDER BY diff DESC LIMIT 10
This is my persons table:
neighborhood birthyear
a 1958
a 1959
b 1970
c 1980
I'd like to get the COUNT of people in an age group within every neighborhood. For example, if I wanted to get everyone under the age of 18, I would get:
neighborhood count
a 0
b 0
c 0
If I wanted to get everyone over 50, I'd get
neighborhood count
a 2
b 0
c 0
I tried
SELECT neighborhood, COUNT(*)
FROM persons
WHERE YEAR(NOW()) - persons.birthyear < 18
GROUP BY neighborhood;
but this gives me 0 rows, when instead I want 3 rows with distinct neighborhoods and 0 count for each. How would I accomplish this?
You can use conditional aggregation:
SELECT neighborhood, SUM(YEAR(NOW()) - p.birthyear) as under_18,
SUM(YEAR(NOW()) - p.birthyear BETWEEN 34 AND 42) as age_34_42
FROM persons p
GROUP BY neighborhood;
I think that if the count is 0, the row doesn't appear.
Your code seems correct to me, if you try it on the example with age 50, it should give you one row whith the expected line (neighborhood:a,count:2)
I would recommend using a sub query:
SELECT
count(*) [group-by-count-greater-than-ten]
FROM
(
SELECT
columnFoo,
count(*) cnt
FROM barTable
WHERE columnBaz = "barbaz"
GROUP BY columnFoo
)
AS subQuery
WHERE cnt > 10
In the above, the subquery return result set is being used by the main query as any other table.
The column cnt is no longer seen by the main query as a computed field and does not have to reference the count() function.
However, inside the subquery running a where clause or a having clause that must look at the alias cnt column, the count() function would have to be referenced as referencing cnt in the subquery would throw an error.
In your case using a subquery would look something like this.
SELECT
neighborhood,
age,
count(*) as cnt
FROM
(
SELECT
*,
(YEAR(NOW()) - birthyear) as age
FROM PERSONS
) as WithAge
WHERE age < 18
GROUP BY neighborhood, age
I want to gather all the details from a table PROD about rows containing particular triplet-sets of values. For example, I want to get all the data on the rows having columns (ID, NBR AND COP_I) with values (23534, 99, 0232) and (3423,5,09384), etc.
I was wondering about a way to select the triplets rows via a Join, which may be better than the way I am doing it below as that currently does not work.
The following Query produces the required triplets, associated with the top 100 rows:
SELECT ID, NBR, COP_I, SUM(PAD_MN) AS PAD_MN_SUMMED
FROM PROD
WHERE
PROD.FLAG = 0
GROUP BY 1,2,3
ORDER BY 4 DESC, 3,2,1
LIMIT 100 --TOP 100 ROWS
I tried joining to the Query above as follows to get all the details corresponding to those top 100 row triplets:
SELECT PROD.ID, PROD.NBR,PROD.COP_I,PROD.FLAG,PROD.TYPE,PROD.DATE, PROD.PAD_MN
FROM ( SELECT ID, NBR, COP_I, SUM(PAD_MN) AS PAD_MN_SUMMED
FROM PROD
WHERE
PROD.FLAG = 0
GROUP BY 1,2,3
ORDER BY 4 DESC, 3,2,1
LIMIT 100) TAB2
INNER JOIN PROD
ON (PROD.ID = TAB2.ID
AND PROD.NBR = TAB2.NBR
AND PROD.COP_I = TAB2.COP_I)
However, the above query gives me rows not even associated with any of the triplets. I feel like I may be making a mistake with the Join, but I don't know why and how to rectify it. I get a similar issue when using the answer provided below
UPDATE
PROD Table containing 10,000+ rows looks something like:
ID NBR COP_I FLAG TYPE DATE PAD_MN
3423 5 09384 0 BA 14-06-2016 18657.43
546 1098 098 1 CFA 22-03-1998 2394566.92
3423 5 09384 0 AA 28-11-2013 3423534.12
23534 99 0232 0 BA 05-01-2016 7304567.12
Results Required, which is to contain only the top 100 rows information:
ID NBR COP_I FLAG TYPE DATE PAD_MN
23534 99 0232 0 BA 05-01-2016 17370567.09
3423 5 09384 0 AA 28-11-2013 6321009.98
However, the output from my query gives rows, which have triplets (ID,NBR,COP_I) which are not actually outputted from the first Query above that produces the required triplets.
If I correctly understand you this is what is you want
with join
select prod.* from (select id, nbr, cop_i, sum(pad_mn) as pad_mn_total from prod where prod.flag = 0 group by 1,2,3 order by 4 desc,3,2,1 limit 100) as top_prod left join prod using (id, nbr, cop_i);
without join
select prod.* from (select id, nbr, cop_i, sum(pad_mn) as pad_mn_total from prod where prod.flag = 0 group by 1,2,3 order by 4 desc,3,2,1 limit 100) as top_prod, prod where prod.id = top_prod.id and prod.nbr = top_prod.nbr and prod.cop_i = top_prod.cop_i;
Better way is to use join. Before using queries in production mode I strongly recommend to check explain response for understanding how data will be collected by mysql and how your indexes works for each query.
Here you can find some info about join http://dev.mysql.com/doc/refman/5.7/en/join.html
How to use explain described here http://dev.mysql.com/doc/refman/5.7/en/using-explain.html
BTW: Reading manuals is a good way to resolve problems
UPD: after some discussions in comments:
Q: Is there a way to prevent these "grouped" rows from being restored whilst still retrieving the other info required only for the 100 sorted rows?
A: select sum(pad_mn) as pad_mn_total, prod.* from prod where prod.flag = 0 group by id,nbr,cop_i order by 1 desc,cop_i,nbr,id limit 100
Problem Statement: I need my result set to include records that would not naturally return because they are NULL.
I'm going to put some simplified code here since my code seems to be too long.
Table Scores has Company_type, Company, Score, Project_ID
Select Score, Count(Project_ID)
FROM Scores
WHERE company_type= :company_type
GROUP BY Score
Results in the following:
Score Projects
5 95
4 94
3 215
2 51
1 155
Everything is working fine until I apply a condition to company_type that does not include results in one of the 5 score categories. When this happens, I don't have 5 rows in my result set any more.
It displays like this:
Score Projects
5 5
3 6
1 3
I'd like it to display like this:
Score Projects
5 5
4 0
3 6
2 0
1 3
I need the results to always display 5 rows. (Scores = 1-5)
I tried one of the approaches below by Spencer7593. My simplified query now looks like this:
SELECT i.score AS Score, IFNULL(count(*), 0) AS Projects
FROM (SELECT 5 AS score
UNION ALL
SELECT 4
UNION ALL
SELECT 3
UNION ALL
SELECT 2
UNION ALL
SELECT 1) i
LEFT JOIN Scores ON Scores.score = i.score
GROUP BY Score
ORDER BY i.score DESC
And gives the following results, which is accurate except that the rows with 1 in Projects should actually be 0 because they are derived by the "i". There are no projects with a score of 5 or 2.
Score Projects
5 1
4 5
3 6
2 1
1 3
Solved! I just needed to adjust my count to specifically look at the project count - count(project) rather than count(*). This returned the expected results.
If you always want your query to return 5 rows, with Score values of 5,4,3,2,1... you'll need a rowsource that supplies those Score values.
One approach would be to use a simple query to return those fixed values, e.g.
SELECT 5 AS score
UNION ALL SELECT 4
UNION ALL SELECT 3
UNION ALL SELECT 2
UNION ALL SELECT 1
Then use that query as inline view, and do an outer join operation to the results from your current query
SELECT i.score AS `Score`
, IFNULL(q.projects,0) AS `Projects`
FROM ( SELECT 5 AS score
UNION ALL SELECT 4
UNION ALL SELECT 3
UNION ALL SELECT 2
UNION ALL SELECT 1
) i
LEFT
JOIN (
-- the current query with "missing" Score rows goes here
-- for completeness of this example, without the query
-- we emulate that result with a different query
SELECT 5 AS score, 95 AS projects
UNION ALL SELECT 3, 215
UNION ALL SELECT 1, 155
) q
ON q.score = i.score
ORDER BY i.score DESC
It doesn't have to be the view query in this example. But there does need to be a rowsource that the rows can be returned from. You could, for example, have a simple table that contains those five rows, with those five score values.
This is just an example approach for the general approach. It might be possible to modify your existing query to return the rows you want. But without seeing the query, the schema, and example data, we can't tell.
FOLLOWUP
Based on the edit to the question, showing an example of the current query.
If we are guaranteed that the five values of Score will always appear in the Scores table, we could do conditional aggregation, writing a query like this:
SELECT s.score
, COUNT(IF(s.company_type = :company_type,s.project_id,NULL)) AS projects
FROM Scores s
GROUP BY s.score
ORDER BY s.score DESC
Note that this will require a scan of all the rows, so it may not perform as well. The "trick" is the IF function, which returns a NULL value in place of project_id, when the row would have been excluded by the WHERE clause.)
If we are guaranteed that project_id is non-NULL, we could use a more terse MySQL shorthand expression to achieve an equivalent result...
, IFNULL(SUM(s.company_type = :company_type),0) AS projects
This works because MySQL returns 1 when the comparison is TRUE, and otherwisee returns 0 or NULL.
Try something like this:
select distinct score
from (
select distinct score from scores
) s
left outer join (
Select Score, Count(Project_ID) cnt
FROM Scores
WHERE company_type= :company_type
) x
on s.score = x.score
Your posted query would not work without a group by statement. However, even there, if you don't have those particular scores for that company type, it wouldn't work either.
One option is to use an outer join. That would require a little more work though.
Here's another option using conditional aggregation:
select Score, sum(company_type=:company_type)
from Scores
group by Score
i am having two tables ss_test and ss_ceastore_config ss_test has field called store_id which maps to ss_ceastore_config id.
my ss_test contains servers entry which tells that which store it is using
so i am trying to find which store is used min times and its id.
i have below query written.
select id,
min(server_counts) as server_counts,
isalive
from (select ss_ceastore_config.id ,
count(server_id)as server_counts,
ss_ceastore_config.isalive
from ss_test
right join ss_ceastore_config
on ss_test.store_id = ss_ceastore_config.id
group by store_id
order by id) join_1
my inner query gives me proper result as below
id Ascending server_counts isalive
1 5 1
2 0 1
so i want to select below record from inner query output using min function
id Ascending server_counts isalive
2 0 1
but it gives unexpected result with my outer query as below
id server_counts isalive
1 0 1
why this so? why it is giving id 1 for server_counts 0?
how to fix this query?
select id,
server_counts,
isalive
from (select ss_ceastore_config.id ,
count(server_id)as server_counts,
ss_ceastore_config.isalive
from ss_test
right join ss_ceastore_config
on ss_test.store_id = ss_ceastore_config.id
group by store_id
order by id) join_1
order by server_counts asc
limit 1;
Your original query was not working because you were doing an aggregate SELECT using the MIN() function along with non-aggregate columns such as id and isalive. I believe that MySQL makes no guarantee about which id value it will return along with the minimum for that column.
My strategy is to return all rows in ascending order by server_counts, and then to SELECT only the first row (which is the minimum).