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Does MySQL ignore null values on unique constraints?
... '1' for key 'x'
INSERT table1 VALUES (NULL);
INSERT table1 VALUES (NULL);
SELECT * FROM table1;
Result:
x
NULL
NULL
1
This is not true for all databases. SQL Server 2005 and older, for example, only allows a single NULL value in a column that has a unique constraint.
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What are the differences between the different saving methods in Hibernate?
...
So in case of detached object, merge will trigger a select whereas update will not ?
– Gab
Mar 17 '14 at 15:44
1
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Check if an apt-get package is installed and then install it if it's not on Linux
... is available
The documentations are also very unclear, e.g.:
sudo apt dselect-upgrade
did not remove certbot when it was marked as deinstall, even though man apt-get seems to indicate that:
dselect-upgrade is used in conjunction with the traditional Debian packaging front-end, dselect(1). ...
Parse string to DateTime in C#
...w[] { "dd-MM-yyyy", "dd.MM.yyyy" };
(new[] { "15-01-2019", "15.01.2019" }).Select(s => s.ToDate(patterns)).Dump();
which will convert the dates in the array on the fly by using the patterns and dump them to the console.
Some background about TryParseExact
Finally, Here are some comments ab...
Differences between Oracle JDK and OpenJDK
...mostly based on HotSpot source code donated by Sun.
Moreover, OpenJDK was selected to be the reference implementation for Java 7 and is maintained by Oracle engineers.
There's a more detailed answer from 2012 on difference between JVM, JDK, JRE & OpenJDK, which links to an Oracle blog post:
...
How to have no pagebreak after \include in LaTeX
...e!
use \include instead of \input, and use the \includeonly command to select sections to process
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Can I have multiple :before pseudo-elements for the same element?
...s the case with any other CSS property.
This behavior is described in the Selectors section of CSS2.1:
Pseudo-elements behave just like real elements in CSS with the exceptions described below and elsewhere.
This implies that selectors with pseudo-elements work just like selectors for normal ...
“PKIX path building failed” and “unable to find valid certification path to requested target”
...pe example.cer
chrome - click on site icon left to address in address bar, select "Certificate" -> "Details" -> "Export" and save in format "Der-encoded binary, single certificate".
Now you have file with keystore and you have to add it to your JVM. Determine location of cacerts files, eg.
C...
The name 'model' does not exist in current context in MVC3
...ew Folder to add the folders. I should have right-clicked the project and selected Add -> Area. Then Visual Studio would have taken care of setting the area up correctly.
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What is Gradle in Android Studio?
... look at these build.gradle files, open Android Studio's Project panel (by selecting the Project tab) and expand the Gradle Scripts folder.
The first two items in the Gradle Scripts folder are the project-level and module-level Gradle build files
Top-Level Gradle Build File
Every Android Studio p...