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How do I modify fields inside the new PostgreSQL JSON datatype?
With postgresql 9.3 I can SELECT specific fields of a JSON data type, but how do you modify them using UPDATE? I can't find any examples of this in the postgresql documentation, or anywhere online. I have tried the obvious:
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Select first row in each GROUP BY group?
As the title suggests, I'd like to select the first row of each set of rows grouped with a GROUP BY .
17 Answers
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SQL - Select first 10 rows only?
How do I select only the first 10 results of a query?
12 Answers
12
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Can I set an unlimited length for maxJsonLength in web.config?
...retrieve the list of more then 17000 records (each won't have more than 10 char length), it's exceeding the length and throws the error:
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Where's my JSON data in my incoming Django request?
...'/event/save-json/',
type: 'POST',
contentType: 'application/json; charset=utf-8',
data: $.toJSON(myEvent),
dataType: 'text',
success: function(result) {
alert(result.Result);
}
});
Django:
def save_events_json(request):
if request.is_ajax():
if request...
Best way to strip punctuation from a string
...or ch in s if ch not in exclude)
This is faster than s.replace with each char, but won't perform as well as non-pure python approaches such as regexes or string.translate, as you can see from the below timings. For this type of problem, doing it at as low a level as possible pays off.
Timing cod...
How do SQL EXISTS statements work?
... criteria -- this is why it can be faster than IN. Also be aware that the SELECT clause in an EXISTS is ignored - IE:
SELECT s.*
FROM SUPPLIERS s
WHERE EXISTS (SELECT 1/0
FROM ORDERS o
WHERE o.supplier_id = s.supplier_id)
...should hit a division by zero error...
UITableView Setting some cells as “unselectable”
How can I set the UITableView's cell property to be unselectable? I don't want to see that blue selection box when the user taps on the cell.
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SQL “select where not in subquery” returns no results
...MySQL
There are three ways to do such a query:
LEFT JOIN / IS NULL:
SELECT *
FROM common
LEFT JOIN
table1 t1
ON t1.common_id = common.common_id
WHERE t1.common_id IS NULL
NOT EXISTS:
SELECT *
FROM common
WHERE NOT EXISTS
(
SELECT NULL
FROM ...
How does a hash table work?
...but strong hashing...
size_t random[8][256] = { ...random data... };
const char* p = (const char*)&my_double;
size_t hash = random[0][(unsigned)p[0]] ^
random[1][(unsigned)p[1]] ^
... ^
random[7][(unsigned)p[7]];
Weak but oft-fast hashing...
Many librar...