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Reference alias (calculated in SELECT) in WHERE clause
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You can't reference an alias except in ORDER BY because SELECT is the second last clause that's evaluated. Two workarounds:
SELECT BalanceDue FROM (
SELECT (InvoiceTotal - PaymentTotal - CreditTotal) AS BalanceDue
FROM Invoices
) AS x
WHERE BalanceDu...
Replace all 0 values to NA
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Replacing all zeroes to NA:
df[df == 0] <- NA
Explanation
1. It is not NULL what you should want to replace zeroes with. As it says in ?'NULL',
NULL represents the null object in R
which is unique and, I guess, can be seen as the most uninformative and empty object...
How to call shell commands from Ruby
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This explanation is based on a commented Ruby script from a friend of mine. If you want to improve the script, feel free to update it at the link.
First, note that when Ruby calls out to a shell, it typically calls /bin/sh, not Ba...
Difference between a Structure and a Union
Is there any good example to give the difference between a struct and a union ?
Basically I know that struct uses all the memory of its member and union uses the largest members memory space. Is there any other OS level difference?
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How can I use goto in Javascript?
I have some code that I absolutely must implement using goto . For example, I want to write a program like this:
16 Answer...
What is the X-REQUEST-ID http header?
...ient can see) with server logs (that the server can see).
The idea of the X-Request-ID is that a client can create some random ID and pass it to the server. The server then include that ID in every log statement that it creates. If a client receives an error it can include the ID in a bug report, a...
Why does Enumerable.All return true for an empty sequence? [duplicate]
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It's certainly not a bug. It's behaving exactly as documented:
true if every element of the source sequence passes the test in the specified predicate, or if the sequence is empty; otherwise, false.
Now you can argue about whether or not it should work that wa...
.NET JIT potential error?
...he inner loop but not updating the oVec.y value properly:
for (oVec.x = 0; oVec.x < 2; oVec.x++) {
0000000a xor esi,esi ; oVec.x = 0
for (oVec.y = 0; oVec.y < 2; oVec.y++) {
0000000c mov edi,2 ; oVec.y = 2, WRON...
Add up a column of numbers at the Unix shell
Given a list of files in files.txt , I can get a list of their sizes like this:
20 Answers
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Is there an expression for an infinite generator?
Is there a straight-forward generator expression that can yield infinite elements?
7 Answers
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