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How to implement the activity stream in a social network
.... Structure so that you can quickly grab a batch of activities by activity ID or by using a set of friend IDs with time constraints.
Publish the activity IDs to Redis whenever an activity record is created, adding the ID to an "activity stream" list for every user who is a friend/subscriber that sho...
Which SQL query is faster? Filter on Join criteria or Where clause?
...
SELECT *
FROM TableA a
LEFT JOIN
TableXRef x
ON x.TableAID = a.ID
AND a.ID = 1
LEFT JOIN
TableB b
ON x.TableBID = b.ID
or this:
SELECT *
FROM TableA a
LEFT JOIN
TableXRef x
ON x.TableAID = a.ID
LEFT JOIN
TableB b
ON b.id = x.Ta...
How to use JavaScript variables in jQuery selectors?
...
var name = this.name;
$("input[name=" + name + "]").hide();
OR you can do something like this.
var id = this.id;
$('#' + id).hide();
OR you can give some effect also.
$("#" + this.id).slideUp();
If you want to remove the entire element permanently form the page.
$("#" ...
When to use Common Table Expression (CTE)
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Interesting fact about CTE. I always wondered why NEWID() in the CTE changes when the CTE is referenced more than once. select top 100 * into #tmp from master..spt_values order by 1,2,3,4 select A.number, COUNT(*) from #tmp A inner join #tmp B ON A.number = B.number+1 group by...
How to click or tap on a TextView text
... to run a method on tapping or clicking a TextView line of text in an Android App.
8 Answers
...
Mysql order by specific ID values
...ible to sort in mysql by "order by" using predefined set of column values (ID) like: order by (ID=1,5,4,3) so I would get record 1, 5, 4, 3 in that order out?
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Rails Model find where not equal
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In Rails 4.x (See http://edgeguides.rubyonrails.org/active_record_querying.html#not-conditions)
GroupUser.where.not(user_id: me)
In Rails 3.x
GroupUser.where(GroupUser.arel_table[:user_id].not_eq(me))
To shorten the length, you could store GroupUser....
MySQL INNER JOIN select only one row from second table
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You need to have a subquery to get their latest date per user ID.
SELECT a.*, c.*
FROM users a
INNER JOIN payments c
ON a.id = c.user_ID
INNER JOIN
(
SELECT user_ID, MAX(date) maxDate
FROM payments
GROUP BY user_ID
) b ON c.user_ID = b....
How to implement one-to-one, one-to-many and many-to-many relationships while designing tables?
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One-to-one: Use a foreign key to the referenced table:
student: student_id, first_name, last_name, address_id
address: address_id, address, city, zipcode, student_id # you can have a
# "link back" if you need
You must also put a unique con...
Django queries - id vs pk
When writing django queries one can use both id/pk as query parameters.
2 Answers
2
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