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Why does NULL = NULL evaluate to false in SQL server
...ee, it is a good idea to avoid NULLs in UNIQUE
constraints.
Discussing GROUP BY:
NULLs are treated as if they were all equal to each other, and
form their own group. Each group is then reduced to a single
row in a new result table that replaces the old one.
This means that for GROUP BY...
What is the difference between supervised learning and unsupervised learning? [closed]
..."invent" what a face is, but it can try to cluster the data into different groups, e.g. it can distinguish that faces are very different from landscapes, which are very different from horses.
Since another answer mentions it (though, in an incorrect way): there are "intermediate" forms of supervisi...
How does the Amazon Recommendation feature work?
...ly, but one component of such an algorithm would probably involve tracking groups of items frequently ordered together, and then using that data to recommend other items in the group when a customer purchases some subset of the group.
Another possibility would be to track the frequency of item B be...
Simple regular expression for a decimal with a precision of 2
... # Require one or more numbers
( # Begin optional group
\. # Point must be escaped or it is treated as "any character"
[0-9]{1,2} # One or two numbers
)? # End group--signify that it's optional with "?"
...
How to see JavaDoc in IntelliJ IDEA? [duplicate]
...
You don’t have to expand the “Editor” menu group. You will not find this setting in one of the its entries. You have to select the Editor “group” itself and it will show a settings page on the right where the option is.
– Matthias Ronge
...
Get names of all keys in the collection
...ert all top key-value pairs into document arrays, followed by $unwind and $group with $addToSet to get distinct keys across the entire collection. (Use $$ROOT for referencing the top level document.)
db.things.aggregate([
{"$project":{"arrayofkeyvalue":{"$objectToArray":"$$ROOT"}}},
{"$unwind":"...
split string only on first instance of specified character
...his example our separator (matching _(.+)) is _luck_buddy and the captured group (within the separator) is lucky_buddy. Without the capturing parenthesis the luck_buddy (matching .+) would've not been included in the result array as it is the case with simple split that separators are not included i...
Finding the id of a parent div using Jquery
...had something already... in my case i used $("#" + id).closest("div.form-group") to find the parent div who had the form-group class.
– cabaji99
May 19 '15 at 13:56
...
typeof for RegExp
...rray] check doesn't work for arrays. See jsfiddle.net/F6d8u for a demo and groups.google.com/group/comp.lang.javascript/browse_frm/thread/… for a discussion of this.
– Tim Down
Dec 3 '10 at 13:28
...
Simple Digit Recognition OCR in OpenCV-Python
... a well defined perfect font. For instance, the digits 0, 4, 6, 9 form one group, the digits 1, 2, 3, 5, 7 form another, and 8 another. This group is given by the euler number. Then "0" has no endpoints, "4" has two, and "6" and "9" are distinguished by centroid position. "3" is the only one, in the...