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Surrogate vs. natural/business keys [closed]
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Remember there is nothing special about a primary key, except that it is labelled as such. It is nothing more than a NOT NULL UNIQUE constraint, and a table can have more than one.
If you use a surrogate key, you still want a business key to ensure uniqueness according to the business rules.
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Is there any significant difference between using if/else and switch-case in C#?
...not strictly O(1) and has noticeable constant costs, but if number of case labels is large, it will be significantly faster than comparing to each string constant in IFs.
To sum it up, if number of conditions is more than 5 or so, prefer SWITCH over IF, otherwise use whatever looks better.
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using facebook sdk in Android studio
...theme="@android:style/Theme.Translucent.NoTitleBar"
android:label="@string/app_name" />
add following in activity_main.xml file :
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_wi...
How to: Define theme (style) item for custom widget
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You can refer to the attribute in a style
<style name="MyDefaultLabelStyle" parent="AppTheme">
<item name="android:background">?background_label</item>
</style>
Notice the question mark, as also used for reference android attribute as in
?android:attr/colorBack...
Android Camera : data intent returns null
...roid:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>...
How to split a column into two columns?
...ders! (I also had to update the link to the docs which explains the (?P<label>...) syntax! I've no idea why I went for the more complex regex, clearly the simple one could work hmmmm
– Andy Hayden
Apr 13 '16 at 1:30
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How to get file creation & modification date/times in Python?
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@MarkAmery - This answer is clearly labeled as just being about modification time.
– ArtOfWarfare
Jan 19 '17 at 18:30
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MaterialDialog 对话框增强扩展 · App Inventor 2 中文网
...为时长参数传入。
WrapContent 自动换行
控制 Toast 内容是否自动换行。设置为 true 则自动换行，设置为 false 则不换行。在调用 ShowToast 之前设置，以控制 Toast 的布局方式。
事件
OnButtonClick 按钮点击时(dialog...
Get statistics for each group (such as count, mean, etc) using pandas GroupBy?
...esult above is a little annoying to deal with because of the nested column labels, and also because row counts are on a per column basis.
To gain more control over the output I usually split the statistics into individual aggregations that I then combine using join. It looks like this:
In [6]: g...
Mean per group in a data.frame [duplicate]
...- structure(list(Name = structure(c(1L, 1L, 1L, 2L, 2L, 2L, 3L,
3L, 3L), .Label = c("Aira", "Ben", "Cat"), class = "factor"),
Month = c(1L, 2L, 3L, 1L, 2L, 3L, 1L, 2L, 3L), Rate1 = c(12L,
18L, 19L, 53L, 22L, 19L, 22L, 67L, 45L), Rate2 = c(23L, 73L,
45L, 19L, 87L, 45L, 87L, 43L, 32L))...