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MySQL select one column DISTINCT, with corresponding other columns
...STINCT results from the FirstName column, but I need the corresponding ID and LastName .
12 Answers
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Do DOM tree elements with ids become global variables?
Working on an idea for a simple HTMLElement wrapper I stumbled upon the following for Internet Explorer and Chrome :
5 An...
Select last row in MySQL
...last of all the rows in the table, then this is finally the time where MAX(id) is the right answer! Kind of:
SELECT fields FROM table ORDER BY id DESC LIMIT 1;
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How to filter SQL results in a has-many-through relation
...fe data.)
Slight diversion from the naming schema in the question: student.id is student.stud_id and club.id is club.club_id here.
I named the queries after their author in this thread, with an index where there are two.
I ran all queries a couple of times to populate the cache, then I picked the be...
How do I perform the SQL Join equivalent in MongoDB?
... The new $lookup operator added to the aggregation pipeline is essentially identical to a left outer join:
https://docs.mongodb.org/master/reference/operator/aggregation/lookup/#pipe._S_lookup
From the docs:
{
$lookup:
{
from: <collection to join>,
localField: <fiel...
Retrieving the last record in each group - MySQL
..._messages AS (
SELECT m.*, ROW_NUMBER() OVER (PARTITION BY name ORDER BY id DESC) AS rn
FROM messages AS m
)
SELECT * FROM ranked_messages WHERE rn = 1;
Below is the original answer I wrote for this question in 2009:
I write the solution this way:
SELECT m1.*
FROM messages m1 LEFT JOIN mes...
What is the difference between save and insert in Mongo DB?
...s essentially the same.
save behaves differently if it is passed with an "_id" parameter.
For save, If the document contains _id, it will upsert querying the collection on the _id field, If not, it will insert.
If a document does not exist with the specified _id value, the save() method performs an...
How to implement Android Pull-to-Refresh
In Android applications such as Twitter (official app), when you encounter a ListView, you can pull it down (and it will bounce back when released) to refresh the content.
...
MySQL Insert into multiple tables? (Database normalization?)
...s (username, password)
VALUES('test', 'test');
INSERT INTO profiles (userid, bio, homepage)
VALUES(LAST_INSERT_ID(),'Hello world!', 'http://www.stackoverflow.com');
COMMIT;
Have a look at LAST_INSERT_ID() to reuse autoincrement values.
Edit: you said "After all this time trying to figure it ...
How to UPSERT (MERGE, INSERT … ON DUPLICATE UPDATE) in PostgreSQL?
...em in useful detail.
In general you must choose between two options:
Individual insert/update operations in a retry loop; or
Locking the table and doing batch merge
Individual row retry loop
Using individual row upserts in a retry loop is the reasonable option if you want many connections concurre...