sql - Relational Algebra -

-

I was wondering if I could get some feedback on relational algebra and if you are looking, Any advice on anything with my SQL may be wrong, you can get it out. 

  Select course course where course no.6 =;

ΠCourseName (σCourseNo = 6 (Course)) 

  CU Choose. C. There is no unit with sys, cu course WHERE C.CourseName = CU.CourseNo and C.CourseName = 'research';

ΠUnitNo (Course Unit (σCourseName = 'Research' (Course)) 

  Select from U.UnitName Student SU StudioUinet, U unit where S. student no .: SU.StudentNo and SU.UnitNo = U.UnitNo and S.StudentName = 'John Perry';

ΠUnitName (Student Unit (Student Unit (σStudentName = 'John Perry' (student))) 

  SELECT count (S. student no) association student from C course Course New = S. Course and N.

ΠResearchStudents ((C) Count (not Student) (Student (ΣCourseName = 'research' (course))

There is a problem with the section, I removed a dot between C. Course 

  SELECT CU from the syllabus, the CU course unit where C. Course name = CU course no and C. course name = 'Research ';

Comments

Post a Comment

Popular posts from this blog

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

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

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