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SQL - HAVING vs. WHERE
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First we should know the order of execution of Clauses i.e
FROM > WHERE > GROUP BY > HAVING > DISTINCT > SELECT > ORDER BY.
Since WHERE Clause gets executed before GROUP BY Clause the records cannot be filtered by applying WHERE to ...
SQL Query to concatenate column values from multiple rows in Oracle
...ommon 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 use SQL Order By statement to sort results case insensitive?
I have a SQLite database that I am trying to sort by Alphabetical order. The problem is, SQLite doesn't seem to consider A=a during sorting, thus I get results like this:
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Rails: Default sort order for a rails model?
I would like to specify a default sort order in my model.
3 Answers
3
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MySQL “Group By” and “Order By”
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A simple solution is to wrap the query into a subselect with the ORDER statement first and applying the GROUP BY later:
SELECT * FROM (
SELECT `timestamp`, `fromEmail`, `subject`
FROM `incomingEmails`
ORDER BY `timestamp` DESC
) AS tmp_table GROUP BY LOWER(`fromEmail`)
This ...
Why should a Java class implement comparable?
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Comparable defines a natural ordering. What this means is that you're defining it when one object should be considered "less than" or "greater than".
Suppose you have a bunch of integers and you want to sort them. That's pretty easy, just put them in a...
Order data frame rows according to vector with specific order
Is there an easier way to ensure that a data frame's rows are ordered according to a "target" vector as the one I implemented in the short example below?
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How do I automatically sort a has_many relationship in Rails?
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You can specify the sort order for the bare collection with an option on has_many itself:
class Article < ActiveRecord::Base
has_many :comments, :order => 'created_at DESC'
end
class Comment < ActiveRecord::Base
belongs_to :article
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Postgres: Distinct but only for one column
...ame. If you want to control which of the rows will be returned you need to order:
select distinct on (name)
name, col1, col2
from names
order by name, col1
Will return the first row when ordered by col1.
distinct on:
SELECT DISTINCT ON ( expression [, ...] ) keeps only the first row of each se...
Select last row in MySQL
...time where MAX(id) is the right answer! Kind of:
SELECT fields FROM table ORDER BY id DESC LIMIT 1;
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