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Reason for Column is invalid in the select list because it is not contained in either an aggregate f
...uld the value of b show on each of these two rows? There are three possibilities in each case, and nothing in the query makes it clear which value to choose for b in each group. It's ambiguous.
This demonstrates the single-value rule, which prohibits the undefined results you get when you run a GRO...
Differences between Exception and Error
...ions are the bread and butter of exception handling. The Javadoc explains it well:
An Error is a subclass of Throwable that indicates serious problems that a
reasonable application should not try to catch. Most such errors are abnormal
conditions.
Look at a few of the subclasses of Error,...
difference between primary key and unique key
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Primary Key:
There can only be one primary key in a table
In some DBMS it cannot be NULL - e.g. MySQL adds NOT NULL
Primary Key is a unique key identifier of the record
Unique Key:
Can be more than one unique key in one table
Unique key can have NULL values
It can be a candidate key
Unique k...
Swapping two variable value without using third variable
...
Using the xor swap algorithm
void xorSwap (int* x, int* y) {
if (x != y) { //ensure that memory locations are different
*x ^= *y;
*y ^= *x;
*x ^= *y;
}
}
Why the test?
The test is to ensure that x and y have diffe...
super() in Java
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super() calls the parent constructor with no arguments.
It can be used also with arguments. I.e. super(argument1) and it will call the constructor that accepts 1 parameter of the type of argument1 (if exists).
Also it can be used to call methods from the parent...
Automatically start forever (node) on system restart
...stem restart. Is there any way I can automatically start the node server (with forever) when the system restarts?
15 Answer...
I don't understand -Wl,-rpath -Wl,
...follow
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edited Mar 1 '18 at 12:51
answered Jul 3 '11 at 10:47
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Parse a .py file, read the AST, modify it, then write back the modified source code
I want to programmatically edit python source code. Basically I want to read a .py file, generate the AST , and then write back the modified python source code (i.e. another .py file).
...
Found conflicts between different versions of the same dependent assembly that could not be resolved
...ts that the build succeeded. However, when I view the Error List Window , it shows me this warning:
22 Answers
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Getting the client's timezone offset in JavaScript
How can I gather the visitor's time zone information? I need the Timezone, as well as the GMT offset hours.
26 Answers
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