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Computed / calculated / virtual / derived columns in PostgreSQL
... Postgres 11 generated columns are not supported - as defined in the SQL standard and implemented by some RDBMS including DB2, MySQL and Oracle. Nor the similar "computed columns" of SQL Server.
STORED generated columns are introduced with Postgres 12. Trivial example:
CREATE TABLE tbl (
int1 ...
How to create a drop-down list?
...
Best way to do it is:
Preview:
XML:
<Spinner
android:id="@+id/spinner1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@android:drawable/btn_dropdown"
android:spinnerMode="dropdown"/>
Java:
//get the sp...
xkcd style graphs in MATLAB
...he various plotting functions I wanted to create a generic tool that could convert any existing plot to a xkcd style plot.
This approach means that you can create plots and style them using standard MATLAB functions and then when you're done you can then re-render the plot in an xkcd style while ...
Retain precision with double in Java
...of 11.4.
Now, a little explanation into why this is happening:
The float and double primitive types in Java are floating point numbers, where the number is stored as a binary representation of a fraction and a exponent.
More specifically, a double-precision floating point value such as the double...
What does {0} mean when initializing an object?
... object, what does it mean? I can't find any references to {0} anywhere, and because of the curly braces Google searches are not helpful.
...
SET versus SELECT when assigning variables?
What are the differences between the SET and SELECT statements when assigning variables in T-SQL?
4 Answers
...
了解 Boost Filesystem Library - C/C++ - 清泛网 - 专注C/C++及内核技术
...int main()
{
boost::filesystem::path path("/usr/local/include"); // random pathname
bool result = boost::filesystem::is_directory(path);
printf(“Path is a directory : %d\n”, result);
return 0;
}
此代码非常明了易懂，您并不需要了解任何系统特定的例程...
MySQL Query - Records between Today and Last 30 Days
...ecords that were added to the database within the last 30 days. I need to convert the date to mm/dd/yy because of display purposes.
...
MySQL foreign key constraints, cascade delete
I want to use foreign keys to keep the integrity and avoid orphans (I already use innoDB).
3 Answers
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How to show math equations in general github's markdown(not github's blog)
...
this worked great. I had to convert a jupyter notebook (.ipynb) to .md and the equations were essentially multiline latex code.
– Marc Maxmeister
Jun 17 '19 at 18:21
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