sql - Should I use Primary key here? -

-

एक उदाहरण के रूप में, मेरे पास 3 टेबल हैं: 

  स्कूल: ID int, नाम Varchar छात्र: ID int, नाम varchar StudentInSchool: StudentID int, SchoolID int

अब सवाल यह है कि मुझे एक कॉलम ID int रखना चाहिए StudentInSchool तालिका में प्राथमिक कुंजी ? यदि हां, तो क्यों?

क्या यह अनुक्रमण करने में सहायक होगा?

कोई भी मदद की सराहना की।

व्यक्तिगत तौर पर, मैं समग्र पीके ( StudentID और SchoolID ) इस तरह तैयार करता हूं। यह विशिष्टता भी सुनिश्चित करता है।

अगर, विशिष्टता की आवश्यकता नहीं है, आपको प्रत्येक पंक्ति को विशिष्ट रूप से पहचानने के लिए एक आईडी कॉलम जोड़ना होगा।

आम तौर पर, एक अलग आईडी कॉलम के अलावा ज्यादा मदद नहीं मिलेगी: बहुत कम प्रश्न (यदि कोई हो) वास्तव में इस कॉलम का उपयोग करेगा। प्रदर्शन के लिए, आप प्रत्येक कॉलम के लिए अलग-अलग अनुक्रमणिका बना सकते हैं और आप बस ठीक हो जाएंगे।


Comments

Post a Comment

Popular posts from this blog

c# - TypeConverter in propertygrid only converts from string, not to -

-
When the property grid is reached, only the conversion mechanism (often called) is called "Foo!" Returns the property string in the grid when I click to edit I get an exception Type.oo. Object type can not be changed to type. (Not properly translated,) What is a clue from the convert format, why not? And the error indicates that it is trying to convert to a string, not from. I think that when I want to edit this object, it will have to be converted from foo to string, and when the editing ends. Public class FooTypeConverter: StringConverter {public override object ConvertFrom (ITypeDescriptorContext Reference, CultureInfo Culture, Object Value) {New Foo (string) value); } Convert the public override object (Type the ITE DiskText Contact Reference, CultureInfo Culture, Object Value, Type Type) {Return "Foo!"; } Public override bool CanConvertFrom (ITypeDescriptorContext reference, type source type) {back true; } Public Override Bull CanConvertTo (ITypeDescrip...
Read more

php - multilevel menu with multilevel array -

-
Just ask someone to solve this problem? I want to create a multilevel menu I can not find the right solution generated with multilevel array, it always gets an array_push error My study came from the original idea But still my Can not match the need. This is my MySQL [code] ----- --------------------- --------------- | ID | PARENT_ID | Name | Link | Seq | 1 | 0 | Dashboad | Dashboard / | 1 | 2 | 0 | Menu 1 | Menu 1 / | 2 | 3 | 0 | Menu 2 | Menu 2 / | 3 | 4 | 0 | Menu 3 | Menu 3 / | 4 | 5 | 2 | Joint Add / | 1 | 6 | 3 | Joint Add / | 1 | 7 | 2 | Edit | Edit / | 2 | 8 | 4 | Joint Add / | 1 ------------------------------------------ [/ Code] I want to do something like this in my array array ('dashboard' = & gt; array ('id' = & gt; '' 'Dame' = & gt; 'Dashboard', 'Title' = & gt; 'Dashboard', 'MatchMin' = & gt; Base_URL (). 'Dashboard /', 'Active' => = & Gt; NULL), ...
Read more

jQuery UI: Datepicker month format -

-
I am trying to change the format of the month that shows in the popup (not in the date that the picker actually I do not have any choice anywhere to do this, do I like to use a sub-string () or something else? What I normally display is Trying to change: Class = "ui-datepicker-title"> January & lt; / span & gt; ... & lt; / div & gt; Div>
Read more