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Select row with most recent date per user
I have a table ("lms_attendance") of users' check-in and out times that looks like this:
11 Answers
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Can I bind an array to an IN() condition?
...'));
$db = new PDO(...);
$stmt = $db->prepare(
'SELECT *
FROM table
WHERE id IN(' . $inQuery . ')'
);
// bindvalue is 1-indexed, so $k+1
foreach ($ids as $k => $id)
$stmt->bindValue(($k+1), $id);
$stmt->execute();
?>
fix: dan, you were right. fixed the code (did...
数据存储组件 · App Inventor 2 中文网
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The callback event for the AddCol block, called once the
values on the table have been updated. Additionally, this returns the
column number for the new column.
FinishedAddRow(rowNumber)
The callback event for the AddRow block, called once the
values on the table have been updated. Additio...
Remove rows with all or some NAs (missing values) in data.frame
...
If performance is a priority, use data.table and na.omit() with optional param cols=.
na.omit.data.table is the fastest on my benchmark (see below), whether for all columns or for select columns (OP question part 2).
If you don't want to use data.table, use comple...
How do you check “if not null” with Eloquent?
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If you wanted to use the DB facade:
DB::table('table_name')->whereNotNull('sent_at')->get();
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How to Implement Custom Table View Section Headers and Footers with Storyboard
...simply drag a UIView onto the canvas, lay it out and then set it in the tableView:viewForHeaderInSection or tableView:viewForFooterInSection delegate methods.
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Why do x86-64 systems have only a 48 bit virtual address space?
...nted hacks do not count as address space in my book. There's no way for portable software to make any use of them.
– R.. GitHub STOP HELPING ICE
Jul 17 '11 at 6:00
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Getting “Lock wait timeout exceeded; try restarting transaction” even though I'm not using a transac
... holding a record lock on some record (you're updating every record in the table!) for too long, and your thread is being timed out.
You can see more details of the event by issuing a
SHOW ENGINE INNODB STATUS
after the event (in sql editor). Ideally do this on a quiet test-machine.
...
How big can a MySQL database get before performance starts to degrade
...data. The most important scalability factor is RAM. If the indexes of your tables fit into memory and your queries are highly optimized, you can serve a reasonable amount of requests with a average machine.
The number of records do matter, depending of how your tables look like. It's a difference ...
INSERT IF NOT EXISTS ELSE UPDATE?
...ot in the insert list will be set to NULL if the row already exists in the table. This is why there's a subselect for the ID column: In the replacement case the statement would set it to NULL and then a fresh ID would be allocated.
This approach can also be used if you want to leave particular fiel...