I have a table with a column named X. X contains number from 0 to 99. But there are duplicates (e.g. 0 is there multiple times! )
Now I need a query that gives any of the rows with 0,1,2,3...99 meaning I get 100 results at with one query, but I don't care which of the x==0 , x==1 ... I get, but just one of them!
Is there such thing in sql?
select distinct x
from your_table
To get a complete record you can group by the X column. But you have to tell the DB which of the duplicate values of the other columns you want.
select x, min(y) as y
from your_table
group by x
If you build a group by X then this value will be distinct. For the other columns you need a so called aggregate function like for example min(). That tells the DB to pick the minimum Y of every X group.
Related
I would like to calculate the mode/median or better, most frequent observation of a categorical variable within my query.
E.g, if the variable has the following string values:
dog, dog, dog, cat, cat and I want to get dog since its 3 vs 2.
Is there any function that does that? I tried APPX_MEDIAN() but it only returns the first 10 characters as median and I do not want that.
Also, I would like to get the most frequent observation with respect to date if there is a tie-break.
Thank you!
the most frequent observation is mode and you can calculate it like this.
Single value mode can be calculated like this on a value column. Get the count and pick up row with max count.
select count(*),value from mytable group by value order by 1 desc limit 1
now, in case you have multiple modes, you need to join back to the main table to find all matches.
select orig.value from
(select count(*) c, value v from mytable) orig
join (select count(*) cmode from mytable group by value order by 1 desc limit 1) cmode
ON orig.c= cmode.cmode
This will get all count of values and then match them based on count. Now, if one value of count matches to max count, you will get 1 row, if you have two value counts matches to max count, you will get 2 rows and so on.
Calculation of median is little tricky - and it will give you middle value. And its not most frequent one.
I would like to filter data by column Base =1 and then count the number of unique values in another column 'Animal' in SQL, data:
Animal Base Value
1 A 1 X
2 B 1 X
3 A 2 Y
4 A 3 V
Expected output in this case is 2 from the first two rows.
Simpler than you may have thought:
SELECT count(DISTINCT Animal)
FROM tbl
WHERE Base = 1;
Should work in any halfway decent RDBMS including your undisclosed one. (You may have to enclose column names in double-quotes.)
This should do it, assuming the table is named animals:
select count(*) from (select distinct Animal from animals where Base=1) tb1;
SELECT x, y, z FROM table_one
WHERE y='asd'
ORDER BY z ASC;
Hi, I'm querying my database using the query above, upon the return of the query I'd like to increment z by 1 (not update it but just increment it so it shows in the result). I don't want to do an Update statement, this is just temporary and should only be visible in the query result.
How would I go about doing this? It's for a school assignment. I've tried to use REPLACE without any success. What works is changing z to z+1 but then the column name changes to ?column? instead of z.
Any help would be appreciated!
You need add column alias:
SELECT x, y, z + 1 AS z -- here
FROM table_one
WHERE y='asd'
ORDER BY z ASC;
I need to write a query that is going to calculate the sum of one column depending on the values of another. Basically I need to get the sum of a certain drug administered for each patient in one of my DB's tables. My table has an account number column (x), drug ID column (y) and an amount administered column (z). The thing is there can be multiple rows for each account number so what I need to do is pull the total amount of that drug administered for each patient account number. So in essence I need a query that will return the sum of z for for every x with a where clause at the end using column y. I hope I am explaining this clearly because thinking about it confuses me! Any help would be appreciated. Thanks guys!
This is a simple GROUP BY query, I'm not sure what's confusing you.
SELECT x, SUM(z) total_z
FROM table
WHERE y = 123
GROUP BY x
Use GROUP BY:
SELECT x, y, sum(z)
FROM t
GROUP by x, y
I have a process that needs to select rows from a Table (queued items) each row has a quantity column and I need to select rows where the quantities add to a specific multiple. The mulitple is the order of between around 4, 8, 10 (but could in theory be any multiple. (odd or even)
Any suggestions on how to select rows where the sum of a field is of a specified multiple?
My first thought would be to use some kind of MOD function which I believe in SQL server is the % sign. So the criteria would be something like this
WHERE MyField % 4 = 0 OR MyField % 8 = 0
It might not be that fast so another way might be to make a temp table containing say 100 values of the X times table (where X is the multiple you are looking for) and join on that