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The SQL OVER() clause - when and why is it useful?
...d why I need it.
What does the function Over do? What does Partitioning By do?
Why can't I make a query with writing Group By SalesOrderID ?
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Is there any difference between GROUP BY and DISTINCT
...ed; the SQL Server is smart enough to realize that if you are using "Group By" and not using any aggregate functions, then what you actually mean is "Distinct" - and therefore it generates an execution plan as if you'd simply used "Distinct."
However, I think it's important to note Hank's response ...
Passing by reference in C
If C does not support passing a variable by reference, why does this work?
17 Answers
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SQL Query to concatenate column values from multiple rows in Oracle
...one is to use LISTAGG:
SELECT pid, LISTAGG(Desc, ' ') WITHIN GROUP (ORDER BY seq) AS description
FROM B GROUP BY pid;
Then join to A to pick out the pids you want.
Note: Out of the box, LISTAGG only works correctly with VARCHAR2 columns.
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How to pass objects to functions in C++?
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Rules of thumb for C++11:
Pass by value, except when
you do not need ownership of the object and a simple alias will do, in which case you pass by const reference,
you must mutate the object, in which case, use pass by a non-const lvalue reference,
you pa...
SQL query to group by day
I want to list all sales, and group the sum by day.
8 Answers
8
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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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