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@UniqueConstraint annotation in Java
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To ensure a field value is unique you can write
@Column(unique=true)
String username;
The @UniqueConstraint annotation is for annotating multiple unique keys at the table level, which is why you get an error when applying it to a field.
References (JPA TopLink):
@UniqueConstraint
@Column
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Make column not nullable in a Laravel migration
... @Musa Apparently you can set a column nullable (ex: $table->string('colmn', 255)->nullable()->change();) but the reverse doesn't appear to work ($table->string('colmn', 255)->change();), so you still need to use raw db queries for this
– Luís Cruz
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slf4j: how to log formatted message, object array, exception
...not recognize that in your example you used n=3 placeholders in the format string and n+1=4 elements in the object array. I had n placeholders in the format string and also n elements in the object array plus an exception as third parameter. My expectation was that the exception would be printed wit...
Difference between single and double quotes in Bash
...or anyone who doesn't know what "interpolate" means: en.wikipedia.org/wiki/String_interpolation
– Kolob Canyon
May 10 '18 at 17:57
1
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Convert int to ASCII and back in Python
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ASCII to int:
ord('a')
gives 97
And back to a string:
in Python2: str(unichr(97))
in Python3: chr(97)
gives 'a'
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PHP: How to send HTTP response code?
...");
Note: According to the HTTP RFC, the reason phrase can be any custom string (that conforms to the standard), but for the sake of client compatibility I do not recommend putting a random string there.
Note: php_sapi_name() requires PHP 4.0.1
3rd argument to header function (PHP >= 4.3)
Th...
Using R to list all files with a specified extension
...- list.files(pattern = "\\.dbf$")
$ at the end means that this is end of string. "dbf$" will work too, but adding \\. (. is special character in regular expressions so you need to escape it) ensure that you match only files with extension .dbf (in case you have e.g. .adbf files).
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What is the difference between 'E', 'T', and '?' for Java generics?
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V - Value
In Java 7 it is permitted to instantiate like this:
Foo<String, Integer> foo = new Foo<>(); // Java 7
Foo<String, Integer> foo = new Foo<String, Integer>(); // Java 6
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Is there a more elegant way of adding an item to a Dictionary safely?
... it's already there, but it doesn't have to be there first:
Dictionary<string, object> currentViews = new Dictionary<string, object>();
currentViews["Customers"] = "view1";
currentViews["Customers"] = "view2";
currentViews["Employees"] = "view1";
currentViews["Reports"] = "view1";
Bas...
SQLite - How do you join tables from different databases?
...lQuery"></param>
public static DataTable GetDataTableFrom2DBFiles(string attachSQL, string sqlQuery)
{
try
{
string conArtistName = "data source=" + path + ";";
using (SQLiteConnection singleConnectionFor2DBFiles = new SQLiteConnection(conArtistName))
{
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