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Unable to cast object of type 'System.DBNull' to type 'System.String`
... the first case @Alexander mentions -not matching any row- you can rely on Convert.ToString or any other Convert method if you are fine with the value they return when converting from null: empty string for strings, 0 for numeric values, false for boolean, MinValue for DateTime... msdn.microsoft.com...
What is the correct SQL type to store a .Net Timespan with values > 24:00:00?
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I'd probably convert the ticks into a time object like this: SELECT CAST(DATEADD(MILLISECOND, @Ticks/CAST(10000 AS BIGINT), '1900-01-01') AS TIME). The '1900-01-01' date doesn't matter, of course, it's just the third variable required by ...
How can I read large text files in Python, line by line, without loading it into memory?
...approximately) that size (in bytes). A negative buffering means to use the system default, which is usually line buffered for tty devices and fully buffered for other files. If omitted, the system default is used
– jyoti das
Apr 19 '18 at 5:26
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How do I prevent an Android device from going to sleep programmatically?
...e a wake lock. Example from the docs:
PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE);
PowerManager.WakeLock wl = pm.newWakeLock(PowerManager.SCREEN_DIM_WAKE_LOCK, "My Tag");
wl.acquire();
// screen and CPU will stay awake during this section
wl.release();
There's also ...
How to calculate percentage with a SQL statement
...ase you overflow on the 100 multiplication (e.g. Arithmetic overflow error converting expression to data type int), replace it with division in denominator instead: cast((count(*) / (sum(count(*)) over() / 100)) AS DECIMAL(18, 2)) as Percentage
– Nikita G.
Jan ...
Installing R on Mac - Warning messages: Setting LC_CTYPE failed, using “C”
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In my system (OS X 10.11 El Capitán) I have environment variables LANG and LC_ALL set to en_US.UTF-8 for my terminal (in the ~/.bash_profile file), and command line R does not display those warning messages; but R Studio does. Fo...
How often does python flush to a file?
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For file operations, Python uses the operating system's default buffering unless you configure it do otherwise. You can specify a buffer size, unbuffered, or line buffered.
For example, the open function takes a buffer size argument.
http://docs.python.org/library/func...
How to correctly implement custom iterators and const_iterators?
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They often forget that iterator must convert to const_iterator but not the other way around. Here is a way to do that:
template<class T, class Tag = void>
class IntrusiveSlistIterator
: public std::iterator<std::forward_iterator_tag, T>
{
typ...
How do I check if an index exists on a table field in MySQL?
...ame) full_path_schema, y.name index_name
FROM information_schema.INNODB_SYS_TABLES as x
JOIN information_schema.INNODB_SYS_INDEXES as y on x.TABLE_ID = y.TABLE_ID
WHERE x.name = 'your_schema'
and y.name = 'your_column') d on concat(a.table_schema, '/', a.table_name, '/', a.column_name) ...
How can I convert a string to a number in Perl?
I have a string which holds a decimal value in it and I need to convert that string into a floating point variable. So an example of the string I have is "5.45" and I want a floating point equivalent so I can add .1 to it. I have searched around the internet, but I only see how to convert a string t...