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Best way to test if a row exists in a MySQL table
I'm trying to find out if a row exists in a table. Using MySQL, is it better to do a query like this:
12 Answers
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Understanding exactly when a data.table is a reference to (vs a copy of) another data.table
I'm having a little trouble understanding the pass-by-reference properties of data.table . Some operations seem to 'break' the reference, and I'd like to understand exactly what's happening.
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Formatting a number with exactly two decimals in JavaScript
I have this line of code which rounds my numbers to two decimal places. But I get numbers like this: 10.8, 2.4, etc. These are not my idea of two decimal places so how I can improve the following?
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List comprehension on a nested list?
I have this nested list:
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Replacing NAs with latest non-NA value
In a data.frame (or data.table), I would like to "fill forward" NAs with the closest previous non-NA value. A simple example, using vectors (instead of a data.frame ) is the following:
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How can I update the current line in a C# Windows Console App?
When building a Windows Console App in C#, is it possible to write to the console without having to extend a current line or go to a new line? For example, if I want to show a percentage representing how close a process is to completion, I'd just like to update the value on the same line as the cur...
How to check if a string “StartsWith” another string?
How would I write the equivalent of C#'s String.StartsWith in JavaScript?
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Difference between variable declaration syntaxes in Javascript (including global variables)?
Is there any difference between declaring a variable:
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Fastest way to check if string contains only digits
I know a few ways how to check this.
regex, int.parse , tryparse ,looping.
18 Answers
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