Is there a SQL function to return the middle value of three?
For example, assume I have a table with people who have three cars, sorted alphabetically by AutoMaker.
John: Ford
John: Honda
John: VW
then
MIN(AutoMaker) returns Ford.
MAX(AutoMaker) returns VW.
Is there a similar SQL function that will return Honda?
I am working with MS Access and Oracle.
Thank you.
Short answer: No. It's too specific.
Longer answer: It's too specific. Hence, the "middle" in what you said is actually the second record. But if you had 5 records, it would be the third, and so on. If you need that in practice, just assign a row number to each row (Oracle, Access) and then select the ((n+1)/2)nd row (WHERE row_number = (n+1)/2).
PS - which is the middle row if you have 4 rows? :)
The query could be something like this
select row_id, Field1
FROM tbl
where row_id = (select cInt(count(Field1)/2) from tbl)
The problem in access is that you do not have a row_number you would need to add a row_id to the table and then populate row_id 1,2,3,4 (ordered on Field1)
Related
All first name should randomly match with each other and when I tried to run query again the First Name should be match with others name. Not the match with FIRST time match.
For example I have 6 records in one table ...
First name column looks like:
JHON
LEE
SAM
HARRY
JIM
KRUK
So I want result like
First name1 First name2
Jhon. Harry
LEE. KRUK
HARRY SAM
The simplest solution is to first randomly sort the records, then calculate the grouping and a sequence number within the group and then finally select out the groups as rows.
You can follow along with the logic in this fiddle: https://dbfiddle.uk/9JlK59w4
DECLARE #Sorted TABLE
(
Id INT PRIMARY KEY,
FirstName varchar(30),
RowNum INT IDENTITY(1,1)
);
INSERT INTO #Sorted (Id, FirstName)
SELECT Id, FirstName
FROM People
ORDER BY NEWID();
WITH Pairs as
(
SELECT *
, (RowNum+1)/2 as PairNum
, RowNum % 2 as Ordinal
FROM #Sorted
)
SELECT
Person1.FirstName as [First name1], Person2.FirstName as [First name2]
FROM Pairs Person1
LEFT JOIN Pairs Person2 ON Person1.PairNum = Person2.PairNum AND Person2.Ordinal = 1
WHERE Person1.Ordinal = 0
ORDER BY Person1.PairNum
ORDER BY NEWID() is used here to randomly sort the records. Note that it is indeterminate and will return a new value with each execution. It's not very efficient, but is suitable for our requirement.
You can't easily use CTE's for producing lists of randomly sorted records because the result of a CTE is not cached. Each time the CTE is referenced in the subsequent logic can result in re-evaluating the expression. Run this fiddle a few times and watch how it often allocates the names incorrectly: https://dbfiddle.uk/rpPdkkAG
Due to the volatility of NEWID() this example stores the results in a table valued variable. For a very large list of records a temporary table might be more efficient.
PairNum uses the simple divide by n logic to assign a group number with a length of n
It is necessary to add 1 to the RowNum because the integer math will round down, see this in action in the fiddle.
Ordinal uses the modulo on the RowNumber and is a value we can use to differentiate between Person 1 and Person 2 in the pair. This helps us keep the rest of the logic determinate.
In the final SELECT we select first from the Pairs that have an Ordinal of 0, then we join on the Pairs that have an Ordinal of 1 matching by the PairNum
You can see in the fiddle I added a solution using groups of 3 to show how this can be easily extended to larger groupings.
I have a table, Ellipses (...), represent multiple columns of a similar type
TABLE: diagnosis_info
COLUMNS: visit_id,
patient_diagnosis_code_1 ...
patient_diagnosis_code_100 -- char(100) with a value of ‘0’ or ‘1’
How do I find the most common diagnosis_code? There are 101 columns including the visit_id. The table is like a matrix table of 0s and 1s. How do I write something that can dynamically account for all the columns and count all the rows where the value is 1?
What I would normally do is not feasable as there are too many columns:
SELECT COUNT(patient_diagnostic_code_1), COUNT(patient_diagnostic_code_2),... FROM diagnostic_info WHERE patient_diagnostic_code_1 = ‘1’ and patient_diagnostic_code_2 = ‘1’ and ….
Then even if I typed all that out how would I select which column had the highest count of values = 1. The table is more column oriented instead of row oriented.
Unfortunately your data design is bad from the start. Instead it could be as simple as:
patient_id, visit_id, diagnosis_code
where a patient with 1 dignostic code would have 1 row, a patient with 100 diagnostic codes 100 rows and vice versa. At any given time you could transpose this into the format you presented (what is called a pivot or cross tab). Also in some databases, for example postgreSQL, you could put all those diagnostic codes into an array field, then it would look like:
patient_id, visit_id, diagnosis_code (data type -bool or int- array)
Now you need the reverse of it which is called unpivot. On some databases like SQL server there is UNPIVOT as an example.
Without knowing what your backend this, you could do that with an ugly SQL like:
select code, pdc
from
(
select 1 as code, count(*) as pdc
from myTable where patient_diagnosis_code_1=1
union
select 2 as code, count(*) as pdc
from myTable where patient_diagnosis_code_2=1
union
...
select 100 as code, count(*) as pdc
from myTable where patient_diagnosis_code_100=1
) tmp
order by pdc desc, code;
PS: This would return all the codes with their frequency ordered from most to least. You could limit to get 1 to get the max (with ties in case there are more than one code to match the max).
How can I return a unique value based on a set of non unique values being searched?
For example:
If I wanted to return one phone number for a list of 4 people who can have more than one phone number - but I can only use one phone number for each person. It doesn't matter which phone number I use to reach them because any number that belongs to them will get me to them.
I don't think something like this exists - but if I could use something like the DISTINCT modifier except it would be called FIRST - it would solve my problem:
SELECT FIRST ID
FROM Sample_Table
WHERE ID in ("Bob", "Sam", "Kyle", "Jordan")
In picture - from this
I'd like that (or any) query to return
.
I'm using this type of query in a db where for 200 "ID"s there are millions of "Unique Values", so it is hard to get crafty.
EDIT The Unique value in my db has numbers and letters in each value
There is no such thing as a "first id" in a SQL table. Tables represent unordered sets. You can accomplish what you want (if I understand correctly) using aggregation:
SELECT ID, MIN(UniqueValue)
FROM Sample_Table
WHERE ID in ('Bob', 'Sam', 'Kyle', 'Jordan')
GROUP BY ID;
using group by and max method can help you:
select id
,uniquvalue
,max (typeofvalue)
from Sample_Table
group by
id
,uniquvalue
I would like to see a most concise way to do what is outlined in this SO question: Sum values from multiple rows into one row
that is, combine multiple rows while summing a column.
But how to then delete the duplicates. In other words I have data like this:
Person Value
--------------
1 10
1 20
2 15
And I want to sum the values for any duplicates (on the Person col) into a single row and get rid of the other duplicates on the Person value. So my output would be:
Person Value
-------------
1 30
2 15
And I would like to do this without using a temp table. I think that I'll need to use OVER PARTITION BY but just not sure. Just trying to challenge myself in not doing it the temp table way. Working with SQL Server 2008 R2
Simply put, give me a concise stmt getting from my input to my output in the same table. So if my table name is People if I do a select * from People on it before the operation that I am asking in this question I get the first set above and then when I do a select * from People after the operation, I get the second set of data above.
Not sure why not using Temp table but here's one way to avoid it (tho imho this is an overkill):
UPDATE MyTable SET VALUE = (SELECT SUM(Value) FROM MyTable MT WHERE MT.Person = MyTable.Person);
WITH DUP_TABLE AS
(SELECT ROW_NUMBER()
OVER (PARTITION BY Person ORDER BY Person) As ROW_NO
FROM MyTable)
DELETE FROM DUP_TABLE WHERE ROW_NO > 1;
First query updates every duplicate person to the summary value. Second query removes duplicate persons.
Demo: http://sqlfiddle.com/#!3/db7aa/11
All you're asking for is a simple SUM() aggregate function and a GROUP BY
SELECT Person, SUM(Value)
FROM myTable
GROUP BY Person
The SUM() by itself would sum up the values in a column, but when you add a secondary column and GROUP BY it, SQL will show distinct values from the secondary column and perform the aggregate function by those distinct categories.
Here is the SQL table:
KEY | NAME | VALUE
---------------------
13b | Jeffrey | 23.5
F48 | Jonas | 18.2
2G8 | Debby | 21.1
Now, if I type:
SELECT *
FROM table
WHERE VALUE = 23.5
I will get the first row.
What I need to accomplish is to get the first and the next two rows below. Is there a way to do it?
Columns are not sorted and WHERE condition doesn't participate in the selection of the rows, except for the first one. I just need the two additional rows below the returned one - the ones that were entered after the one which has been returned by the SELECT query.
Without a date column or an auto-increment column, you can't reliably determine the order the records were entered.
The physical order with which rows are stored in the table is non-deterministic.
You need to define an order to the results to do this. There is no guaranteed order to the data otherwise.
If by "the next 2 rows after" you mean "the next 2 records that were inserted into the table AFTER that particular row", you will need to use an auto incrementing field or a "date create" timestamp field to do this.
If each row has an ID column that is unique and auto incrementing, you could do something like:
SELECT * FROM table WHERE id > (SELECT id FROM table WHERE value = 23.5)
If I understand correctly, you're looking for something like:
SELECT * FROM table WHERE value <> 23.5
You can obviously write a program to do that but i am assuming you want a query. What about using a Union. You would also have to create a new column called value_id or something in those lines which is incremented sequentially (probably use a sequence). The idea is that value_id will be incremented for every insert and using that you can write a where clause to return the remaining two values you want.
For example:
Select * from table where value = 23.5
Union
Select * from table where value_id > 2 limit 2;
Limit 2 because you already got the first value in the first query
You need an order if you want to be able to think in terms of "before" and "after".
Assuming you have one you can use ROW_NUMBER() (see more here http://msdn.microsoft.com/en-us/library/ms186734.aspx) and do something like:
With MyTable
(select row_number() over (order by key) as n, key, name, value
from table)
select key, name, value
from MyTable
where n >= (select n from MyTable where value = 23.5)