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MySQL select one column DISTINCT, with corresponding other columns
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try this query
SELECT ID, FirstName, LastName FROM table GROUP BY(FirstName)
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Are there benefits of passing by pointer over passing by reference in C++?
What are the benefits of passing by pointer over passing by reference in C++?
7 Answers
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data.table vs dplyr: can one do something well the other can't or does poorly?
...m data.table perspective.
Note: unless explicitly mentioned otherwise, by referring to dplyr, we refer to dplyr's data.frame interface whose internals are in C++ using Rcpp.
The data.table syntax is consistent in its form - DT[i, j, by]. To keep i, j and by together is by design. By keeping ...
Oracle “Partition By” Keyword
Can someone please explain what the partition by keyword does and give a simple example of it in action, as well as why one would want to use it? I have a SQL query written by someone else and I'm trying to figure out what it does.
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SQL RANK() versus ROW_NUMBER()
...partition and within that partition the first 3 rows are tied when ordered by ID)
WITH T(StyleID, ID)
AS (SELECT 1,1 UNION ALL
SELECT 1,1 UNION ALL
SELECT 1,1 UNION ALL
SELECT 1,2)
SELECT *,
RANK() OVER(PARTITION BY StyleID ORDER BY ID) AS 'RANK',
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How to use DISTINCT and ORDER BY in same SELECT statement?
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The problem is that the columns used in the ORDER BY aren't specified in the DISTINCT. To do this, you need to use an aggregate function to sort on, and use a GROUP BY to make the DISTINCT work.
Try something like this:
SELECT DISTINCT Category, MAX(CreationDate)
FROM Mon...
How to order by with union in SQL?
... < 15
Union
Select id,name,age
From Student
Where Name like "%a%"
Order by name
the order by is applied to the complete resultset
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SQL - HAVING vs. WHERE
... hence HAVING works correctly.
As a rule of thumb, use WHERE before GROUP BY and HAVING after GROUP BY. It is a rather primitive rule, but it is useful in more than 90% of the cases.
While you're at it, you may want to re-write your query using ANSI version of the join:
SELECT L.LectID, Fname, L...
Why should the copy constructor accept its parameter by reference in C++?
Why must a copy constructor's parameter be passed by reference?
8 Answers
8
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Using LIMIT within GROUP BY to get N results per group?
..._CONCAT aggregated function to get all years into a single column, grouped by id and ordered by rate:
SELECT id, GROUP_CONCAT(year ORDER BY rate DESC) grouped_year
FROM yourtable
GROUP BY id
Result:
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| ID | GROUPED_YEAR ...