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Rails 3: Get Random Record
... big tables but more sql-style
UPD. You can use the following trick on an indexed column (PostgreSQL syntax):
select *
from my_table
where id >= trunc(
random() * (select max(id) from my_table) + 1
)
order by id
limit 1;
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How to find and return a duplicate value in array
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Simply find the first instance where the index of the object (counting from the left) does not equal the index of the object (counting from the right).
arr.detect {|e| arr.rindex(e) != arr.index(e) }
If there are no duplicates, the return value will be nil.
I be...
How to use the 'main' parameter in package.json?
...meter in your package.json if the entry point to your package differs from index.js in its root folder. For example, people often put the entry point to lib/index.js or lib/<packagename>.js, in this case the corresponding script must be described as main in package.json.
You can't have two scr...
How do I modify fields inside the new PostgreSQL JSON datatype?
... create_missing boolean default true)
path can contain JSON array indexes too & negative integers that appear there count from the end of JSON arrays. However, a non-existing, but positive JSON array index will append the element to the end of the array:
SELECT jsonb_set('{"a":[null,{"b...
How can I make SQL case sensitive string comparison on MySQL?
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@adjwilli If the column was a part of an index, you will suffer a performance hit on queries reliant on that index. To maintain performance, you need to actually alter the table.
– dshin
Sep 19 '13 at 18:50
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Java using enum with switch statement
I've looked at various Q&As on SO similar to this question but haven't found a solution.
8 Answers
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How to list containers in Docker
... ls -a
And then, if you want to clean them all,
docker rm $(docker ps -aq)
It is used to list all the containers created irrespective of its state.
And to stop all the Docker containers (force)
docker rm -f $(docker ps -a -q)
Here the container is the management command.
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MySQL order by before group by
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For scaling, the compound INDEX(post_author, post_date) is important.
– Rick James
Mar 1 '15 at 16:08
1
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Convert DOS line endings to Linux line endings in Vim
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@ropata What you want on Windows is ctrl-q.
– ruffin
Aug 31 '16 at 16:28
3
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how do I insert a column at a specific column index in pandas?
Can I insert a column at a specific column index in pandas?
4 Answers
4
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