aggregate-functions

Is there a proper way to aggregate a single column when I have many other columns in the query? I've tried this answer which works, but my query has become a lot more verbose. My current query looks like this: SELECT t1.foo1, t1.foo2, t2.foo3, t2.foo4, string_agg(t3.aggregated_field, ', ') FROM tbl1 t1 LEFT JOIN tbl2 t2 ON t1.id = t2.fkeyid LEFT JOIN tbl3 t3 ON t2.id = t3.fkeyid GROUP BY t1.foo1, t1.foo2, t2.foo3, t2.foo4, t2.foo5, t2.foo6 ORDER BY t2.foo5, t2.foo6 The query has many more fields and LEFT JOIN s, the important part is that all these fields have 1 to 1 or 1 to 0 relationship

I have created a RelationalGroupedDataset by calling instances.groupBy(instances.col("property_name")) : val x = instances.groupBy(instances.col("property_name")) How do I compose a user-defined aggregate function to perform Statistics.colStats().mean on each group? Thanks! user6910411 Spark >= 2.4 You can use Summarizer : import org.apache.spark.ml.stat.Summarizer val dfNew = df.as[(Int, org.apache.spark.mllib.linalg.Vector)] .map { case (group, v) => (group, v.asML) } .toDF("group", "features") dfNew .groupBy($"group") .agg(Summarizer.mean($"features").alias("means")) .show(false) +-----+---

I need function, that returns list of strings. I have data in table like this: Id MyString ------------------------ 1 First 2 Second 3 Third 4 Fourth I need function like this (something like this works in oracle): select LISTAGG(MyString, ', ') as myList where id < 4 That returns something like this: myList ------------------------ First, Second, Third Any ideas? You're looking for GROUP_CONCAT() Try this: select group_concat(MyString separator ', ') as myList from table where id < 4 Of course, you can group by the results. As of MySQL 5.7.22 you can also use two JSON aggregation functions:

I'm sure this has been asked but I can't quite find the right search terms. Given a schema like this: | CarMakeID | CarMake ------------------------ | 1 | SuperCars | 2 | MehCars | CarMakeID | CarModelID | CarModel ----------------------------------------- | 1 | 1 | Zoom | 2 | 1 | Wow | 3 | 1 | Awesome | 4 | 2 | Mediocrity | 5 | 2 | YoureSettling I want to produce a dataset like this: | CarMakeID | CarMake | CarModels --------------------------------------------- | 1 | SuperCars | Zoom, Wow, Awesome | 2 | MehCars | Mediocrity, YoureSettling What do I do in place of 'AGG' for strings in SQL

I know that if you have one aggregate function in a SELECT statement, then all the other values in the statement must be either aggregate functions, or listed in a GROUP BY clause. I don't understand why that's the case. If I do: SELECT Name, 'Jones' AS Surname FROM People I get: NAME SURNAME Dave Jones Susan Jones Amy Jones So, the DBMS has taken a value from each row, and appended a single value to it in the result set. That's fine. But if that works, why can't I do: SELECT Name, COUNT(Name) AS Surname FROM People It seems like the same idea, take a value from each row and append a single

My app has a Events table with time-stamped events. I need to report the count of events during each of the most recent N time intervals. For different reports, the interval could be "each week" or "each day" or "each hour" or "each 15-minute interval". For example, a user can display how many orders they received each week, day, or hour, or quarter-hour. 1) My preference is to dynamically do a single SQL query (I'm using Postgres) that groups by an arbitrary time interval. Is there a way to do that? 2) An easy but ugly brute force way is to do a single query for all records within the start

I am trying to understand GROUP BY (new to oracle dbms) without aggregate function. How does it operate? Here is what i have tried. EMP table on which i will run my SQL. SELECT ename , sal FROM emp GROUP BY ename , sal SELECT ename , sal FROM emp GROUP BY ename; Result ORA-00979: not a GROUP BY expression 00979. 00000 - "not a GROUP BY expression" *Cause: *Action: Error at Line: 397 Column: 16 SELECT ename , sal FROM emp GROUP BY sal; Result ORA-00979: not a GROUP BY expression 00979. 00000 - "not a GROUP BY expression" *Cause: *Action: Error at Line: 411 Column: 8 SELECT empno , ename , sal