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How do I create a unique constraint that also allows nulls?
...contains null values for this columns. How do I create the constraint that allows multiple null values?
14 Answers
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Add Foreign Key to existing table
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To add a foreign key (grade_id) to an existing table (users), follow the following steps:
ALTER TABLE users ADD grade_id SMALLINT UNSIGNED NOT NULL DEFAULT 0;
ALTER TABLE users ADD CONSTRAINT fk_grade_id FOREIGN KEY (grade_id) REFERENCES grades(id);
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From io.Reader to string in Go
...byte to a string, you could change the contents of the string. However, go allows you to disable the type safety mechanisms using the unsafe package. Use the unsafe package at your own risk. Hopefully the name alone is a good enough warning. Here is how I would do it using unsafe:
buf := new(bytes....
Current time in microseconds in java
...ble on many platforms, 2) returning millisecond accuracy in a microsecond call leads to application portability issues.
– Stephen C
Nov 11 '09 at 4:17
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ScalaTest in sbt: is there a way to run a single test without tags?
...ldcard, you could specify the full path com.example.specs.YourTestClass.)
All tests within that test class will be executed. Presumably you're most concerned with failing tests, so correct any failing implementations and then run:
test:testQuick
... which will only execute tests that failed. (Re...
How to restore to a different database in sql server?
...mpCopy with the contents of your.bak.
Example (restores a backup of a db called 'creditline' to 'MyTempCopy';
RESTORE FILELISTONLY FROM DISK='e:\mssql\backup\creditline.bak'
>LogicalName
>--------------
>CreditLine
>CreditLine_log
RESTORE DATABASE MyTempCopy FROM DISK='e:\mssql\backu...
How can I give eclipse more memory than 512M?
I have following setup, but when I put 1024 and replace all 512 with 1024, then eclipse won't start at all. How can I have more than 512M memory for my eclipse JVM?
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Remove icon/logo from action bar on android
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If you've defined android:logo="..." in the <application> tag of your AndroidManifest.xml, then you need to use this stuff to hide the icon:
pre-v11 theme
<item name="logo">@android:color/transparent</item>
v11 and up theme
<item name="android:logo...
instantiate a class from a variable in PHP?
...you work with namespace, put the current namespace into the string: $var = __NAMESPACE__ . '\\' . $var . 'Class';
– bastey
Sep 2 '13 at 13:28
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Getting the error “Java.lang.IllegalStateException Activity has been destroyed” when using tabs with
I have an application that consists of using ActionBarSherlock in tab mode.I have 5 tabs and the content of each tab is handled using fragments. For tab2 though, I have a fragment the xml file of which holds a ViewPager element which in turn has some fragment pages. When I initially start the applic...