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mongodb group values by multiple fields
...takes an "pipeline" expression as an argument instead of the "localFields" and "foreignFields" options. This then allows a "self-join" with another pipeline expression, in which we can apply $limit in order to return the "top-n" results.
db.books.aggregate([
{ "$group": {
"_id": "$addr",
"...
How to delete from multiple tables in MySQL?
...m trying to delete from a few tables at once. I've done a bit of research, and came up with this
7 Answers
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How to check which locks are held on a table
...first block that caused the other blocks.
Edit to add comment from @MikeBlandford:
The blocked column indicates the spid of the blocking process. You can run kill {spid} to fix it.
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im...
How to specify id when uses include in layout xml file
...out xml file, I have included other layout xml file (each
with a different android id).
11 Answers
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What is the standard naming convention for html/css ids and classes?
...oks like I like to mix things up yearly... After switching to Sublime Text and using Bootstrap for a while, I've gone back to dashes. To me now they look a lot cleaner than un_der_scores or camelCase. My original point still stands though: there isn't a standard.
Update 2015
An interesting corner ...
SQL WHERE ID IN (id1, id2, …, idn)
...
Option 3 is simply horrible performance-wise. It sends a query every loop and hammers the database with small queries. It also prevents it from using any optimizations for "value is one of those in a given list"
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MySQL foreign key constraints, cascade delete
I want to use foreign keys to keep the integrity and avoid orphans (I already use innoDB).
3 Answers
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Handling colon in element ID with jQuery
...xplanation:
Apart from the speed gain (see further down), it is easier to handle.
Example: Say you have a function
function doStuff(id){
var jEle = $("#" + id); //is not safe, since id might be "foo:bar:baz" and thus fail.
//You would first have to look for ":" in the id string,...
Can I use CASE statement in a JOIN condition?
.... From the image we can see that the relationship between sys.partitions and sys.allocation_units depends on the value of sys.allocation_units.type . So to join them together I would write something similar to this:
...
Android OnClickListener - identify a button
...b1);
b2 = (Button) findViewById(R.id.b2);
b1.setOnClickListener(myhandler1);
b2.setOnClickListener(myhandler2);
...
}
View.OnClickListener myhandler1 = new View.OnClickListener() {
public void onClick(View v) {
// it was the 1st button
}
};
View.OnClickListener ...