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MySQL Conditional Insert
... AND item = 456)
In this, dual is a table with one row only (found originally in Oracle, now in mysql too). The logic is that the SELECT statement generates a single row of data with the required values, but only when the values are not already found.
Alternatively, look at the MERGE statement.
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React.js: onChange event for contentEditable
...hich fixes a bug in my implementation.
Use the onInput event, and optionally onBlur as a fallback. You might want to save the previous contents to prevent sending extra events.
I'd personally have this as my render function.
var handleChange = function(event){
this.setState({html: event.ta...
What is the role of the bias in neural networks? [closed]
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I think that biases are almost always helpful. In effect, a bias value allows you to shift the activation function to the left or right, which may be critical for successful learning.
It might help to look at a simple example. Consider this 1-input, 1-output network that has no bias:
The ou...
How do I detect the Python version at runtime? [duplicate]
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@iBug is correct. The documentation specifically says to instead use sys.version_info for our purpose here. docs.python.org/3/library/sys.html#sys.version
– Max Barraclough
Jan 1 at 19:06
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Getting and removing the first character of a string
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x <- 'hello stackoverflow'
substring(x, 2, nchar(x))
Idea is select all characters starting from 2 to number of characters in x. This is important when you have unequal number of characters in word or phrase.
Selecting the first letter is trivial as previous answers:
substring(x,1,1)
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How to do joins in LINQ on multiple fields in single join
...xplain that reason.
If you want to do something other than what you originally asked for, please give an example of what you really want to do.
EDIT: Responding to the edit in the question: yes, to do a "date range" join, you need to use a where clause instead. They're semantically equivalent real...
What's the difference between VARCHAR and CHAR?
...your content is a fixed size" it means the rows of your table must contain all fixed size fields. You get no performance improvement if you use CHAR against VARCHAR in one field, but the table contains other fields that are VARCHAR.
– Marco Demaio
May 20 '10 at...
Aggregate / summarize multiple variables per group (e.g. sum, mean)
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what if I instead of x1 and x2 I want to use all the remaining variables (other than year, month)
– Clock Slave
Mar 16 '16 at 11:22
8
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Generating a list of which files changed between hg versions
... consider using the "x::y" (DAG - Directed Acyclic Graph) range.
Given parallel changesets,
1--2---4
\---3
hg status --rev 1:4 would return (1,2,3,4),
i.e. anything between and including the endpoints, according to the local, numerical rev. This might (and most probably will) return different...
How to do multiple arguments to map function where one remains the same in python?
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@Shan: Very similar, especially if add() is a non-trivial function
– Sven Marnach
May 31 '12 at 13:52
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