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How do I add a foreign key to an existing SQLite table?
...
SQLite doesn't support the ADD CONSTRAINT variant of the ALTER TABLE command (sqlite.org: SQL Features That SQLite Does Not Implement).
Therefore, the only way to add a foreign key in sqlite 3.6.1 is during CREATE TABLE as follows:
CREATE TABLE child (
id INTEGER PRIMARY KEY,
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'is' versus try cast with null check
... below the belt. Take a look at this example:
object o = "test";
if (o is string)
{
var x = (string) o;
}
This translates to the following IL:
IL_0000: nop
IL_0001: ldstr "test"
IL_0006: stloc.0 // o
IL_0007: ldloc.0 // o
IL_0008: isinst System.String
IL_000D...
Best way to find the intersection of multiple sets?
...lving reduce. It can in general be used quite nicely to build lists, sets, strings etc. Worth a look also is github.com/EntilZha/PyFunctional
– Andreas
Nov 16 '16 at 6:03
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How to check whether a file or directory exists?
...exists returns whether the given file or directory exists
func exists(path string) (bool, error) {
_, err := os.Stat(path)
if err == nil { return true, nil }
if os.IsNotExist(err) { return false, nil }
return false, err
}
Edited to add error handling.
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How do I display the current value of an Android Preference in the Preference summary?
...public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) {
Preference pref = findPreference(key);
if (pref instanceof ListPreference) {
ListPreference listPref = (ListPreference) pref;
pref.setSummary(listPref.getEntry());
}
}
This is easi...
How to find duplicates in 2 columns not 1
...composite key between the two fields. This will require a unique stone_id and upcharge_title for each row.
As far as finding the existing duplicates try this:
select stone_id,
upcharge_title,
count(*)
from your_table
group by stone_id,
upcharge_title
having coun...
JavaScript and Threads
...ol API
WHATWG has a Draft Recommendation for worker threads: Web Workers
And there's also Mozilla’s DOM Worker Threads
Update: June 2009, current state of browser support for JavaScript threads
Firefox 3.5 has web workers. Some demos of web workers, if you want to see them in action:
Simu...
SQLite DateTime comparison
...reliable results from the query against a sqlite database using a datetime string as a comparison as so:
12 Answers
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How do I access my SSH public key?
I've just generated my RSA key pair, and I wanted to add that key to GitHub.
18 Answers
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Rails find_or_create_by more than one attribute?
There is a handy dynamic attribute in active-record called find_or_create_by:
5 Answers
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