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nvarchar和varchar相互转换、联合查询 - ORACLE - 清泛IT论坛，有思想、有深度
...要对数据类型进行转换。
Specifying the USING CHAR_CS argument converts text into the database character set. The output datatype is VARCHAR2.
Specifying the USING NCHAR_CS argument converts text into the national character set. The output datatype is NVARCHAR2.
（A表字段c_xxx:varc...
Measuring execution time of a function in C++
... When I use this function, on first run it gave me 118440535 microseconds and on second run of the same function it gave me 83221031 microseconds. Shouldn't the two time measurements be equal when I am measuring the duration of that function only ?
– Xara
Mar ...
Combine two ActiveRecord::Relation objects
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Relation objects can be converted to arrays. This negates being able to use any ActiveRecord methods on them afterwards, but I didn't need to. I did this:
name_relation = first_name_relation + last_name_relation
Ruby 1.9, rails 3.2
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Export database schema into SQL file
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Right click the database you want to generate scripts for (not the table) and select tasks - generate scripts
Next, select the requested table/tables, views, stored procedures, etc (from select specific database objects)
Click advanced - select the types of data to script
Click Next and finish
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How to sort in-place using the merge sort algorithm?
...s the array xs, the two sorted sub-arrays are represented as ranges [i, m) and [j, n) respectively. The working area starts from w. Compare with the standard merge algorithm given in most textbooks, this one exchanges the contents between the sorted sub-array and the working area. As the result, the...
Guid is all 0's (zeros)?
I'm testing out some WCF services that send objects with Guids back and forth. In my web app test code, I'm doing the following:
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How do you determine the size of a file in C?
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You could probably change the return type to ssize_t and cast the size from an off_t without any trouble. It would seem to make more sense to use a ssize_t :-) (Not to be confused with size_t which is unsigned and cannot be used to indicate error.)
– Ted P...
Is there a string math evaluator in .NET?
...gests the builtin DataTable.Compute-"trick". Here it is.
double result = Convert.ToDouble(new DataTable().Compute("1 + 2 * 7", null));
The following arithmetic operators are supported in expressions:
+ (addition)
- (subtraction)
* (multiplication)
/ (division)
% (modulus)
More informations: D...
How can I check if a string is null or empty in PowerShell?
... null strings passed to a commandlet or function don't stay null. They get converted to empty strings. See the Microsoft Connect bug at connect.microsoft.com/PowerShell/feedback/details/861093/….
– JamieSee
Dec 11 '14 at 17:59
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Rails migration for change column
...l situations where the existing data, let's say a String can be implicitly converted into the new datatype, let's say Date.
In this situation, it's helpful to know you can create migrations with data conversions. Personally, I like putting these in my model file, and then removing them after all d...