I have the following table:
SequenceNumber are always a multiple of 10. I would like to get, for a specific cpId, the smallest free sequence number (still in a multiple of 10). For example, for cpId = 1, the smallest available should be 20. For cpId = 2, it should be 10.
I have the following statement to get the smallest available sequenceNumber for all cpId, and I don't know how I can add a WHERE cpId = x inside the statement:
SELECT MIN(t1.sequenceNumber + 10) AS nextID
FROM LogicalConnection t1
LEFT JOIN LogicalConnection t2
ON t1.sequenceNumber + 10 = t2.sequenceNumber
WHERE t2.sequenceNumber IS NULL;
DB fiddle: https://www.db-fiddle.com/f/ag67AkFzfwPZEva8bTN7Q3/2#&togetherjs=L9nHb3Uu7O
Thank you for your help!
You can use lead() to get the next number and then some simple logic:
select cpid,
(case when min_sn > 10 then 10
else min(sequenceNumber) + 10
end)
from (select t.*,
min(sequenceNumber) over (partition by cpid) as min_sn,
lead(sequenceNumber) over (partition by cpid order by sequenceNumber) as next_sn
from t
) t
where next_sn is null or next_sn <> sequenceNumber + 10
group by cpid, min_sn;
You have to join both tables on cpId column and group the rows with similar cpId.
Where can be used to filter rows.
Below query gives you the cpId and their corresponding next available minimum sequence number.
SELECT t1.cpId, MIN(t1.sequenceNumber + 10) AS nextID
FROM LogicalConnection t1
LEFT JOIN LogicalConnection t2
ON t1.sequenceNumber + 10 = t2.sequenceNumber
and t1.cpId = t2.cpId
group by (t1.cpId)
Related
I need to fetch 12 questions from my table. I have a field called "bucket" which might have duplicate values.
While fetching, I need only unique bucket values to be fetched and the number of rows has to be 12.
This is my query:
select *
from (
select
DISTINCT ON (q.bucket) bucket,
row_number() over (partition by dl.value order by random()) as rn,
row_number() over (partition by dl.value, LOWER(qc.value) = LOWER('general') order by random()) as rnc,
dl.value, qc.value as question_category,
q.question_text, q.option_a, q.option_b, q.option_c, q.option_d,
q.correct_answer, q.image_link, q.question_type
from
questions_bank q
inner join
question_category qc on qc.id = q.question_category_id
inner join
sports_type st on st.id = q.sports_type_id
inner join
difficulty_level dl on dl.id = q.difficulty_level_id
where st.game_type = lower('cricket') and dl.value in ('E','M','H')
) s
where
(value = 'E' and rnc <= 3 and LOWER(question_category) != LOWER('general')) or
(value = 'E' and rnc <= 3 and LOWER(question_category) = LOWER('general')) or
value = 'M' and rn <= 4 or
value = 'H' and rn <= 2;
Can anyone please tell me what am I doing wrong here? It sometimes doesn't return 12 rows. This happens whenever a same bucket value is found. I think, whenever distinct is applied that duplicate row's value is removed. Hence, when I do rn<=4 it is not able to find say, 3. Thus returning only 3 rows instead of 4.
So, I need to apply distinct on bucket first and then get row_numbers. How shall I do that?
How can you select the top n max values from a table?
For a table like this:
column1 column2
1 foo
2 foo
3 foo
4 foo
5 bar
6 bar
7 bar
8 bar
For n=2, the result needs to be:
3
4
7
8
The approach below selects only the max value for each group.
SELECT max(column1) FROM table GROUP BY column2
Returns:
4
8
For n=2 you could
SELECT max(column1) m
FROM table t
GROUP BY column2
UNION
SELECT max(column1) m
FROM table t
WHERE column1 NOT IN (SELECT max(column1)
WHERE column2 = t.column2)
for any n you could use approaches described here to simulate rank over partition.
EDIT:
Actually this article will give you exactly what you need.
Basically it is something like this
SELECT t.*
FROM
(SELECT grouper,
(SELECT val
FROM table li
WHERE li.grouper = dlo.grouper
ORDER BY
li.grouper, li.val DESC
LIMIT 2,1) AS mid
FROM
(
SELECT DISTINCT grouper
FROM table
) dlo
) lo, table t
WHERE t.grouper = lo.grouper
AND t.val > lo.mid
Replace grouper with the name of the column you want to group by and val with the name of the column that hold the values.
To work out how exactly it functions go step-by-step from the most inner query and run them.
Also, there is a slight simplification - the subquery that finds the mid can return NULL if certain category does not have enough values so there should be COALESCE of that to some constant that would make sense in the comparison (in your case it would be MIN of domain of the val, in article it is MAX).
EDIT2:
I forgot to mention that it is the LIMIT 2,1 that determines the n (LIMIT n,1).
If you are using mySQl, why don't you use the LIMIT functionality?
Sort the records in descending order and limit the top n i.e. :
SELECT yourColumnName FROM yourTableName
ORDER BY Id desc
LIMIT 0,3
Starting from MySQL 8.0/MariaDB support window functions which are designed for this kind of operations:
SELECT *
FROM (SELECT *,ROW_NUMBER() OVER(PARTITION BY column2 ORDER BY column1 DESC) AS r
FROM tab) s
WHERE r <= 2
ORDER BY column2 DESC, r DESC;
DB-Fiddle.com Demo
This is how I'm getting the N max rows per group in MySQL
SELECT co.id, co.person, co.country
FROM person co
WHERE (
SELECT COUNT(*)
FROM person ci
WHERE co.country = ci.country AND co.id < ci.id
) < 1
;
how it works:
self join to the table
groups are done by co.country = ci.country
N elements per group are controlled by ) < 1 so for 3 elements - ) < 3
to get max or min depends on: co.id < ci.id
co.id < ci.id - max
co.id > ci.id - min
Full example here:
mysql select n max values per group/
mysql select max and return multiple values
Note: Have in mind that additional constraints like gender = 0 should be done in both places. So if you want to get males only, then you should apply constraint on the inner and the outer select
I currently have the code below and it works for getting me the 2 smallest number, but I want to get all of the 2nd smallest numbers and link them to their name as opposed to just one of them. lets say the numbers in the tables was made up of this:
Name| number
----|------
w 2
a 8
s 2
e 2
z 3
I would want to get
w 2
s 2
e 2
and now I am just getting w 2
SELECT MAX(col) FROM table WHERE col NOT IN (SELECT MAX(col) FROM table);
If this code gets you the second smallest number (what you want):
SELECT MAX(col) FROM table WHERE col NOT IN (SELECT MAX(col) FROM table);
Then simply do:
select *
from table
where col = (SELECT MAX(col) FROM table WHERE col NOT IN (SELECT MAX(col) FROM table));
I didn't understand well, but if you're using LIMIT 1,1, you will only get 1 row or none.
Just use what #491243 commented on your question.
SELECT * FROM tablename WHERE number = (SELECT MIN(number) FROM tableName);
Forget it, now I understood the question.
Try this:
SELECT * FROM tablename WHERE number =
(SELECT number FROM tablename WHERE number !=
(SELECT MIN(number) FROM tablename) ORDER BY number LIMIT 1);
Hope this helps.
EDIT: Using the SQLFiddle table:
SELECT * FROM ships WHERE gunsize = (
SELECT gunsize FROM ships WHERE gunsize !=
(SELECT MIN(gunsize) FROM ships) ORDER BY gunsize LIMIT 1);
http://sqlfiddle.com/#!2/9ca94/11
SELECT name,(SELECT MAX(gunsize) FROM ships s2
WHERE s2.Name=s.name and gunsize not in (select max(gunsize) from ships))as gunsizes
FROM ships s
Something like this?
I have a MySQL table from which I want to select:
1) Either "most occurring" value, if there is any prevailing
2) Or "average" value, if there is no most occurring value.
Example table 1:
value
1
2
3
4
All values are occurred equally, therefore I want to take AVG(`value`)
Example table 2:
value
1
2
2
3
Value 2 prevails, therefore I want to select the value 2.
What mysql query would do this?
Starting from Gordon's answer I tested and corrected the SQL query in SQL Fiddle:
SELECT IF(t4.numcnts = 1, t1.avgvalue, t2.topvalue) AS result
FROM (select avg(value) as avgvalue from test) t1
CROSS JOIN (select value as topvalue from test group by value order by count(*) desc limit 1) t2
CROSS JOIN join (select count(distinct cnt) as numcnts from
(select count(*) as cnt from test group by value) t3) t4
Here is the Fiddle with the two test tables (switch out test2 for test to see the result when a particular value prevails): http://sqlfiddle.com/#!2/76914/3
My changes were to use an IF instead of a CASEstatement in the SELECTclause and to add the necessary table aliases for the subselects.
The following approach calculates both values and then chooses between them:
select (case when numcnts = 1 then avgvalue else topvalue end)
from (select avg(value) as avgvalue from t) cross join
(select value as topvalue from t group by value order by count(*) desc limit 1) cross join
(select count(distinct cnt) as numcnts from (select count(*) as cnt from t group by value))
Note: if you have ties for the top, but other values as well, then an arbitrary value is returned. You don't specify what to do in this case.
Also, the SQL is untested, so it might have syntax errors.
How can you select the top n max values from a table?
For a table like this:
column1 column2
1 foo
2 foo
3 foo
4 foo
5 bar
6 bar
7 bar
8 bar
For n=2, the result needs to be:
3
4
7
8
The approach below selects only the max value for each group.
SELECT max(column1) FROM table GROUP BY column2
Returns:
4
8
For n=2 you could
SELECT max(column1) m
FROM table t
GROUP BY column2
UNION
SELECT max(column1) m
FROM table t
WHERE column1 NOT IN (SELECT max(column1)
WHERE column2 = t.column2)
for any n you could use approaches described here to simulate rank over partition.
EDIT:
Actually this article will give you exactly what you need.
Basically it is something like this
SELECT t.*
FROM
(SELECT grouper,
(SELECT val
FROM table li
WHERE li.grouper = dlo.grouper
ORDER BY
li.grouper, li.val DESC
LIMIT 2,1) AS mid
FROM
(
SELECT DISTINCT grouper
FROM table
) dlo
) lo, table t
WHERE t.grouper = lo.grouper
AND t.val > lo.mid
Replace grouper with the name of the column you want to group by and val with the name of the column that hold the values.
To work out how exactly it functions go step-by-step from the most inner query and run them.
Also, there is a slight simplification - the subquery that finds the mid can return NULL if certain category does not have enough values so there should be COALESCE of that to some constant that would make sense in the comparison (in your case it would be MIN of domain of the val, in article it is MAX).
EDIT2:
I forgot to mention that it is the LIMIT 2,1 that determines the n (LIMIT n,1).
If you are using mySQl, why don't you use the LIMIT functionality?
Sort the records in descending order and limit the top n i.e. :
SELECT yourColumnName FROM yourTableName
ORDER BY Id desc
LIMIT 0,3
Starting from MySQL 8.0/MariaDB support window functions which are designed for this kind of operations:
SELECT *
FROM (SELECT *,ROW_NUMBER() OVER(PARTITION BY column2 ORDER BY column1 DESC) AS r
FROM tab) s
WHERE r <= 2
ORDER BY column2 DESC, r DESC;
DB-Fiddle.com Demo
This is how I'm getting the N max rows per group in MySQL
SELECT co.id, co.person, co.country
FROM person co
WHERE (
SELECT COUNT(*)
FROM person ci
WHERE co.country = ci.country AND co.id < ci.id
) < 1
;
how it works:
self join to the table
groups are done by co.country = ci.country
N elements per group are controlled by ) < 1 so for 3 elements - ) < 3
to get max or min depends on: co.id < ci.id
co.id < ci.id - max
co.id > ci.id - min
Full example here:
mysql select n max values per group/
mysql select max and return multiple values
Note: Have in mind that additional constraints like gender = 0 should be done in both places. So if you want to get males only, then you should apply constraint on the inner and the outer select