I have a database as shown below
id , name , var1
and I want to write a sql query like this:
select name
from table
where last var1 > avg of var1 s of each name
Notice that i want to select between names that last var1 is greater than avrage of var1s of each name
i write this code :
select name
from table
where var1>(select avg(var1) from table ) limit 0 , 1
but this code gets avrage from all var1s and I dont know whether this works or not!
for example we have these data:
1 , John , 32
2 , John , 21
3 , Mike , 22
4 , John , 11
5 , Mike , 5
6 , Mike , 45
=> for John , we have: 32+21+11 /3 =21.3 , but the last data is 11 , so John shouldnt be chosen
=> for Mike , avrage of var1 is 24 , and last row for Mike is 45 that is greater than the avrage , so Mike should be chosen.
Can anyone help me?
SELECT y.* FROM
your_table y
JOIN
(
SELECT name, AVG(var1) AS av, MAX(id) AS mx
FROM your_table
GROUP BY name
) tab
ON y.name = tab.name
AND y.id = tab.mx
AND y.var1 > tab.av
Here is the code at SQL Fiddle
[EDIT]:
Based on your latest requirement, what you want to accomplish is LIMIT N within group, which can be done with the following query:
SET #N := 2;
SELECT * FROM
(
SELECT (#rownumber:= #rownumber + 1) AS rn, yt.*
FROM your_table yt,(SELECT #rownumber:= 0) nums
ORDER BY name, id
) k
JOIN
(
SELECT t.name, MAX(rn) AS MaxRN FROM
(
SELECT (#rownumber:= #rownumber + 1) AS rn, yt.*
FROM your_table yt,(SELECT #rownumber:= 0) nums
ORDER BY name, id
) t
GROUP BY name
) l
ON k.rn <= l.MaxRN AND k.rn > l.MaxRN - #N
Here #N variable holds number of records we want to select within each group
Check the code at SQL Fiddle
Now in an outer query we can take the avg of the resultset returned by above.
Let me know if you could accomplish what you wanted with my inputs.
Related
Lets say I have a table of product price history, which is the price and product id, with the following records:
id price
1 23
2 14
2 23
2 20
3 30
3 40
what I want is to show the data grouped by id, showing the prices at which has been sold each product.
What i expectis something like this:
id priceA PriceB PriceC
1 23 NULL NULL
2 14 23 20
3 30 40 NULL
This is not the right way to do things
you should use a separate table and try some primary keys.
suppose you have a poductprice table with id and price
make a view like
CREATE VIEW history AS (
SELECT
id,
CASE WHEN id = "1" THEN price END AS priceA,
CASE WHEN id = "2" THEN price END AS priceB,
CASE WHEN id = "3" THEN price END AS priceC
FROM productprice
);
SELECT * FROM history;
This requirement really a bad fit for SQL, but it can be achieved with a lot of fiddling involving "dynamic sql" and fudges to achieve te equivalent of row_number(). i.e. It would be easier to achieve with CTE and row_number() perhaps if MySQL gets bith this could be revisited.
Anyway, what is required is getting the prices into numbered columns, so the first price of each product goes in the first column, the second price in the second column and so on. So we need in the first instance a way to number the rows which will later be transformed into columns. In MySQL this can be done by using variables, like this:
select
#row_num := IF(#prev_value = p.id, #row_num+1, 1) AS RowNumber
, id
, price
, #prev_value := p.id
from (select distinct id, price from pricehistory) p
CROSS JOIN ( SELECT #row_num :=1, #prev_value :='' ) vars
order by id, price
So that snippet is used twice in the following. In the upper part it forms a set of case expressions that will do the transformation. I the lower part we combine those case expressions with the remainder of the wanted sql and then execute it.
set #sql = (
SELECT GROUP_CONCAT(col_ref)
FROM (
select distinct
concat(' max(case when RowNumber=',RowNumber,' then Price else NULL end) as c',RowNumber) col_ref
from (
select
#row_num := IF(#prev_value = p.id, #row_num+1, 1) AS RowNumber
, id
, price
, #prev_value := p.id
from (select distinct id, price from pricehistory) p
CROSS JOIN ( SELECT #row_num :=1, #prev_value :='' ) vars
order by id, price
) d
order by `RowNumber`
) dc
);
set #sql = concat('select id,', #sql,
' from (
select
#row_num := IF(#prev_value = p.id, #row_num+1, 1) AS RowNumber
, id
, price
, #prev_value := p.id
from (select distinct id, price from pricehistory) p
CROSS JOIN ( SELECT #row_num :=1, #prev_value :='''' ) vars
order by id, price
) d
Group By `id`');
#select #sql
PREPARE stmt FROM #sql;
EXECUTE stmt;
\\
The result of this, based on the sample given is:
id c1 c2 c3
1 1 23 NULL NULL
2 2 14 20 23
3 3 30 40 NULL
This solution can be tested and re-run at: http://rextester.com/AYAA36866
Note the fully generated sql reads like this:
select id
, max(case when RowNumber=1 then Price else NULL end) as c1
, max(case when RowNumber=2 then Price else NULL end) as c2
, max(case when RowNumber=3 then Price else NULL end) as c3
from (
select
#row_num := IF(#prev_value = p.id, #row_num+1, 1) AS RowNumber
, id
, price
, #prev_value := p.id
from (select distinct id, price from pricehistory) p
CROSS JOIN ( SELECT #row_num :=1, #prev_value :='' ) vars
order by id, price
) d
Group By `id`
You might want something like this:
SELECT id, GROUP_CONCAT(string SEPARATOR ' ') FROM priceHistory GROUP BY id;
So I was taking a test recently with some higher level SQL problems. I only have what I would consider "intermediate" experience in SQL and I've been working on this for a day or so now. I just can't figure it out.
Here's the problem:
You have a table with 4 columns as such:
EmployeeID int unique
EmployeeType int
EmployeeSalary int
Created date
Goal: I need to retrieve the difference between the latest two EmployeeSalary for any EmployeeType with more than 1 entry. It has to be done in one statement (nested queries are fine).
Example Data Set: http://sqlfiddle.com/#!9/0dfc7
EmployeeID | EmployeeType | EmployeeSalary | Created
-----------|--------------|----------------|--------------------
1 | 53 | 50 | 2015-11-15 00:00:00
2 | 66 | 20 | 2014-11-11 04:20:23
3 | 66 | 30 | 2015-11-03 08:26:21
4 | 66 | 10 | 2013-11-02 11:32:47
5 | 78 | 70 | 2009-11-08 04:47:47
6 | 78 | 45 | 2006-11-01 04:42:55
So for this data set, the proper return would be:
EmployeeType | EmployeeSalary
-------------|---------------
66 | 10
78 | 25
The 10 comes from subtracting the latest two EmployeeSalary values (30 - 20) for the EmployeeType of 66. The 25 comes from subtracting the latest two EmployeeSalary values (70-45) for EmployeeType of 78. We skip EmployeeID 53 completely because it only has one value.
This one has been destroying my brain. Any clues?
Thanks!
How to make really simple query complex?
One funny way(not best performance) to do it is:
SELECT final.EmployeeType, SUM(salary) AS difference
FROM (
SELECT b.EmployeeType, b.EmployeeSalary AS salary
FROM tab b
JOIN (SELECT EmployeeType, GROUP_CONCAT(EmployeeSalary ORDER BY Created DESC) AS c
FROM tab
GROUP BY EmployeeType
HAVING COUNT(*) > 1) AS sub
ON b.EmployeeType = sub.EmployeeType
AND FIND_IN_SET(b.EmployeeSalary, sub.c) = 1
UNION ALL
SELECT b.EmployeeType, -b.EmployeeSalary AS salary
FROM tab b
JOIN (SELECT EmployeeType, GROUP_CONCAT(EmployeeSalary ORDER BY Created DESC) AS c
FROM tab
GROUP BY EmployeeType
HAVING COUNT(*) > 1) AS sub
ON b.EmployeeType = sub.EmployeeType
AND FIND_IN_SET(b.EmployeeSalary, sub.c) = 2
) AS final
GROUP BY final.EmployeeType;
SqlFiddleDemo
EDIT:
The keypoint is MySQL doesn't support windowed function so you need to use equivalent code:
For example solution in SQL Server:
SELECT EmployeeType, SUM(CASE rn WHEN 1 THEN EmployeeSalary
ELSE -EmployeeSalary END) AS difference
FROM (SELECT *,
ROW_NUMBER() OVER(PARTITION BY EmployeeType ORDER BY Created DESC) AS rn
FROM #tab
) AS sub
WHERE rn IN (1,2)
GROUP BY EmployeeType
HAVING COUNT(EmployeeType) > 1
LiveDemo
And MySQL equivalent:
SELECT EmployeeType, SUM(CASE rn WHEN 1 THEN EmployeeSalary
ELSE -EmployeeSalary END) AS difference
FROM (
SELECT t1.EmployeeType, t1.EmployeeSalary,
count(t2.Created) + 1 as rn
FROM #tab t1
LEFT JOIN #tab t2
ON t1.EmployeeType = t2.EmployeeType
AND t1.Created < t2.Created
GROUP BY t1.EmployeeType, t1.EmployeeSalary
) AS sub
WHERE rn IN (1,2)
GROUP BY EmployeeType
HAVING COUNT(EmployeeType) > 1;
LiveDemo2
The dataset of the fiddle is different from the example above, which is confusing (not to mention a little perverse). Anyway, there's lots of ways to skin this particular cat. Here's one (not the fastest, however):
SELECT a.employeetype, ABS(a.employeesalary-b.employeesalary) diff
FROM
( SELECT x.*
, COUNT(*) rank
FROM employees x
JOIN employees y
ON y.employeetype = x.employeetype
AND y.created >= x.created
GROUP
BY x.employeetype
, x.created
) a
JOIN
( SELECT x.*
, COUNT(*) rank
FROM employees x
JOIN employees y
ON y.employeetype = x.employeetype
AND y.created >= x.created
GROUP
BY x.employeetype
, x.created
) b
ON b.employeetype = a.employeetype
AND b.rank = a.rank+1
WHERE a.rank = 1;
a very similar but faster solution looks like this (although you sometimes need to assign different variables between tables a and b - for reasons I still don't fully understand)...
SELECT a.employeetype
, ABS(a.employeesalary-b.employeesalary) diff
FROM
( SELECT x.*
, CASE WHEN #prev = x.employeetype THEN #i:=#i+1 ELSE #i:=1 END i
, #prev := x.employeetype prev
FROM employees x
, (SELECT #prev := 0, #i:=1) vars
ORDER
BY x.employeetype
, x.created DESC
) a
JOIN
( SELECT x.*
, CASE WHEN #prev = x.employeetype THEN #i:=#i+1 ELSE #i:=1 END i
, #prev := x.employeetype prev
FROM employees x
, (SELECT #prev := 0, #i:=1) vars
ORDER
BY x.employeetype
, x.created DESC
) b
ON b.employeetype = a.employeetype
AND b.i = a.i + 1
WHERE a.i = 1;
I need to be able to do something with my column (below) that can contain multiple values. The 'HearAboutEvent' column has multiple values separated by a comma. Each one of these values corresponds to an entry in another table. So the value of 11273 will equal facebook, 11274 will mean radio, and 11275 will mean commercial.
The data I am working with looks like this:
weather ID MemberID SubscriptionID DateEntered ParticipatedBefore ParticipatedBeforeCities WeatherDependent NonRefundable TShirtSize HearAboutEvent
Yes 24 18 1 2013-12-19 0 NULL 10950 10952 10957 11273, 11274, 11275
I am able to do the proper join to resolve the value of 'weather', note it is the first column and the 8th column.
This is the query I have created so far to resolve the values of WeatherDependent:
SELECT CFS1.Name as 'weather', *
FROM FSM_CustomForm_693 t
LEFT JOIN FSM_CustomFormSelectOptions CFS1 ON CFS1.ID = t.WeatherDependent
where t.ID = 24
Ultimately I need to have the data look like this:
weather ID MemberID SubscriptionID DateEntered ParticipatedBefore ParticipatedBeforeCities WeatherDependent NonRefundable TShirtSize HearAboutEvent
Yes 24 18 1 2013-12-19 0 NULL 10950 10952 10957 Facebook, radio, commercial
Things I think you could use to accomplish this are:
A Split TVF FUNCTION - http://msdn.microsoft.com/en-us/library/ms186755.aspx
CROSS APPLY - http://technet.microsoft.com/en-us/library/ms175156.aspx
STUFF & FOR XML PATH - http://msdn.microsoft.com/en-us/library/ms188043.aspx & http://msdn.microsoft.com/en-us/library/ms190922.aspx
Going one step further, you need something like this:
Excuse my profuse use of sub queries.
CREATE FUNCTION dbo.Split (#sep char(1), #s varchar(512))
RETURNS table
AS
RETURN (
WITH Pieces(pn, start, stop) AS (
SELECT 1, 1, CHARINDEX(#sep, #s)
UNION ALL
SELECT pn + 1, stop + 1, CHARINDEX(#sep, #s, stop + 1)
FROM Pieces
WHERE stop > 0
)
SELECT pn,
SUBSTRING(#s, start, CASE WHEN stop > 0 THEN stop-start ELSE 512 END) AS s
FROM Pieces
)
GO
SELECT
O.A,O.B,O.C,O.D,O.E,O.F,O.G,O.H,O.I,O.J,O.Stuffed
FROM (
SELECT
*
,STUFF((
SELECT ', ' + Name
FROM (
SELECT
V.*
,Y.Name
FROM (
SELECT
'Yes' AS A
,24 AS B
,18 AS C
,1 AS D
,'2013-12-19' AS E
,0 AS F
,NULL AS G
,10950 AS H
,10952 AS I
,10957 AS J
,'11273, 11274, 11275' AS K
)
AS V
CROSS APPLY dbo.Split(',',REPLACE(K,' ','')) AS P
JOIN (
SELECT 11273 AS Id , 'Facebook' AS Name UNION ALL
SELECT 11274 AS Id , 'radio' AS Name UNION ALL
SELECT 11275 AS Id , 'commercial' AS Name
)Y ON y.Id = p.s) ExampleTable
FOR XML PATH('')
), 1, 1, '' )
AS [Stuffed]
FROM (
SELECT
V.*
FROM (
SELECT
'Yes' AS A
,24 AS B
,18 AS C
,1 AS D
,'2013-12-19' AS E
,0 AS F
,NULL AS G
,10950 AS H
,10952 AS I
,10957 AS J
,'11273, 11274, 11275' AS K
)
AS V
CROSS APPLY dbo.Split(',',REPLACE(K,' ','')) AS P
JOIN (
SELECT 11273 AS Id , 'Facebook' AS Name UNION ALL
SELECT 11274 AS Id , 'radio' AS Name UNION ALL
SELECT 11275 AS Id , 'commercial' AS Name
)Y ON y.Id = p.s
)Z
) O
GROUP BY O.A,O.B,O.C,O.D,O.E,O.F,O.G,O.H,O.I,O.J,O.K,O.Stuffed
This question already has answers here:
How to get next/previous record in MySQL?
(23 answers)
Closed 4 years ago.
I have the following table, named Example:
id(int 11) //not autoincriment
value (varchar 100)
It has the following rows of data:
0 100
2 150
3 200
6 250
7 300
Note that id values are not contiguous.
I've written this SQL so far:
SELECT * FROM Example WHERE id = 3
However, I don't know how to get the value of previous id and value of the next id...
Please help me get previous value and next value if id = 3 ?
P.S.: in my example it will be: previous - 150, next - 250.
Select the next row below:
SELECT * FROM Example WHERE id < 3 ORDER BY id DESC LIMIT 1
Select the next row above:
SELECT * FROM Example WHERE id > 3 ORDER BY id LIMIT 1
Select both in one query, e.g. use UNION:
(SELECT * FROM Example WHERE id < 3 ORDER BY id DESC LIMIT 1)
UNION
(SELECT * FROM Example WHERE id > 3 ORDER BY id LIMIT 1)
That what you mean?
A solution would be to use temporary variables:
select
#prev as previous,
e.id,
#prev := e.value as current
from
(
select
#prev := null
) as i,
example as e
order by
e.id
To get the "next" value, repeat the procedure. Here is an example:
select
id, previous, current, next
from
(
select
#next as next,
#next := current as current,
previous,
id
from
(
select #next := null
) as init,
(
select
#prev as previous,
#prev := e.value as current,
e.id
from
(
select #prev := null
) as init,
example as e
order by e.id
) as a
order by
a.id desc
) as b
order by
id
Check the example on SQL Fiddle
May be overkill, but it may help you
please try this sqlFiddle
SELECT value,
(SELECT value FROM example e2
WHERE e2.value < e1.value
ORDER BY value DESC LIMIT 1) as previous_value,
(SELECT value FROM example e3
WHERE e3.value > e1.value
ORDER BY value ASC LIMIT 1) as next_value
FROM example e1
WHERE id = 3
Edit: OP mentioned to grab value of previous id and value of next id in one of the comments so the code is here SQLFiddle
SELECT value,
(SELECT value FROM example e2
WHERE e2.id < e1.id
ORDER BY id DESC LIMIT 1) as previous_value,
(SELECT value FROM example e3
WHERE e3.id > e1.id
ORDER BY id ASC LIMIT 1) as next_value
FROM example e1
WHERE id = 3
SELECT *,
(SELECT value FROM example e1 WHERE e1.id < e.id ORDER BY id DESC LIMIT 1 OFFSET 0) as prev_value,
(SELECT value FROM example e2 WHERE e2.id > e.id ORDER BY id ASC LIMIT 1 OFFSET 0) as next_value
FROM example e
WHERE id=3;
And you can place your own offset after OFFSET keyword if you want to select records with higher offsets for next and previous values from the selected record.
Here's my solution may suit you:
SELECT * FROM Example
WHERE id IN (
(SELECT MIN(id) FROM Example WHERE id > 3),(SELECT MAX(id) FROM Example WHERE id < 3)
)
Demo: http://sqlfiddle.com/#!9/36c1d/2
A possible solution if you need it all in one row
SELECT t.id, t.value, prev_id, p.value prev_value, next_id, n.value next_value
FROM
(
SELECT t.id, t.value,
(
SELECT id
FROM table1
WHERE id < t.id
ORDER BY id DESC
LIMIT 1
) prev_id,
(
SELECT id
FROM table1
WHERE id > t.id
ORDER BY id
LIMIT 1
) next_id
FROM table1 t
WHERE t.id = 3
) t LEFT JOIN table1 p
ON t.prev_id = p.id LEFT JOIN table1 n
ON t.next_id = n.id
Sample output:
| ID | VALUE | PREV_ID | PREV_VALUE | NEXT_ID | NEXT_VALUE |
|----|-------|---------|------------|---------|------------|
| 3 | 200 | 2 | 150 | 4 | 250 |
Here is SQLFiddle demo
This query uses a user defined variable to calculate the distance from the target id, and a series of wrapper queries to get the results you want. Only one pass is made over the table, so it should perform well.
select * from (
select id, value from (
select *, (#x := ifnull(#x, 0) + if(id > 3, -1, 1)) row from (
select * from mytable order by id
) x
) y
order by row desc
limit 3
) z
order by id
See an SQLFiddle
If you don't care about the final row order you can omit the outer-most wrapper query.
If you do not have an ID this has worked for me.
Next:
SELECT * FROM table_name
WHERE column_name > current_column_data
ORDER BY column_name ASC
LIMIT 1
Previous:
SELECT * FROM table_name
WHERE column_name < current_column_data
ORDER BY column_name DESC
LIMIT 1
I use this for a membership list where the search is on the last name of the member. As long as you have the data from the current record it works fine.
I have a table as following:
NAME SCORE
-----------------
willy 1
willy 2
willy 3
zoe 4
zoe 5
zoe 6
Here's the sample
The aggregation function for group by only allow me to get the highest score for each name.
I would like to make a query to get the highest 2 score for each name, how should I do?
My expected output is
NAME SCORE
-----------------
willy 2
willy 3
zoe 5
zoe 6
SELECT *
FROM test s
WHERE
(
SELECT COUNT(*)
FROM test f
WHERE f.name = s.name AND
f.score >= s.score
) <= 2
SQLFiddle Demo
In MySQL, you can use user-defined variables to get a row number in each group:
select name, score
from
(
SELECT name,
score,
(#row:=if(#prev=name, #row +1, if(#prev:= name, 1, 1))) rn
FROM test123 t
CROSS JOIN (select #row:=0, #prev:=null) c
order by name, score desc
) src
where rn <= 2
order by name, score;
See Demo
If you don't mind having additional column then you can use the following code:
SELECT Name, Score, rank() over(partition by Name order by Score DESC) as rank
From Table
Having rank < 3;
Rank function provides rank for each partition, in your case it is name
insert into test values('willy',1)
insert into test values('willy',2)
insert into test values('willy',3)
insert into test values('zoe',4)
insert into test values('zoe',5)
insert into test values('zoe',6)
;with temp_cte
as (
select Name, Score,
ROW_NUMBER() OVER (
PARTITION BY Name
ORDER BY Score desc
) row_num
from test
)
select * from temp_cte
where row_num < 3
For this you can do this-
http://www.sqlfiddle.com/#!2/ee665/4
but in order to get first 2 query, you should use a ID then run limit for ID like 0,2.
You can do somthething like this:
SET #num :=0, #name :='';
SELECT name, score,
#num := IF( #name= name, #num +1, 1 ) AS row_number,
#name := name AS dummy
FROM test
GROUP BY name, score
HAVING row_number <=2
SELECT * FROM (
SELECT VD.`cat_id` ,
#cat_count := IF( (#cat_id = VD.`cat_id`), #cat_count + 1, 1 ) AS 'DUMMY1',
#cat_id := VD.`cat_id` AS 'DUMMY2',
#cat_count AS 'CAT_COUNT'
FROM videos VD
INNER JOIN categories CT ON CT.`cat_id` = VD.`cat_id`
,(SELECT #cat_count :=1, #cat_id :=-1) AS CID
ORDER BY VD.`cat_id` ASC ) AS `CAT_DETAILS`
WHERE `CAT_COUNT` < 4
------- STEP FOLLOW ----------
1 . select * from ( 'FILTER_DATA_HERE' ) WHERE 'COLUMN_COUNT_CONDITION_HERE'
2. 'FILTER_DATA_HERE'
1. pass 2 variable #cat_count=1 and #cat_id = -1
2. If (#cat_id "match" column_cat_id value)
Then #cat_count = #cat_count + 1
ELSE #cat_count = 1
3. SET #cat_id = column_cat_id
3. 'COLUMN_COUNT_CONDITION_HERE'
1. count_column < count_number
4. ' EXTRA THING '
1. If you want to execute more than one statement inside " if stmt "
2. IF(condition, stmt1 , stmt2 )
1. stmt1 :- CONCAT(exp1, exp2, exp3)
2. stmt2 :- CONCAT(exp1, exp2, exp3)
3. Final "If" Stmt LIKE
1. IF ( condition , CONCAT(exp1, exp2, exp3) , CONCAT(exp1, exp2, exp3) )
Use this query.
select * from fruits
where type = 'orange'
order by price limit 2
Solution Here:
https://www.xaprb.com/blog/2006/12/07/how-to-select-the-firstleastmax-row-per-group-in-sql/