title: plsqldeveloper: update records in table, if a condition about the records is satisfied in another table
body: <p>i'v been working this problem for hours now, but can't get the hang of it.
  i have a rather big project about the topic in school, so i provided here with a simple example. please help me understand the best approach here:</p>
  
  <p>for students i have a table "Student" with info about the students, including student_id and student_birthdate.</p>
  
  <p>for courses i have a table "Course" with course_id, course_name and so on.</p>
  
  <p>for the grades of the students in each course, i have a "CourseStudent" table, containing: student_id, course_id, and grade, which is the grade of the student in this course.</p>
  
  <p>i need to update the grades (in the "CourseStudent" table) like this:
  any student that was born after 1990, i want to add 3 points to his grades, but only his grades that are above 50.</p>
  
  <p>i tried cursors, loops and functions, but when i do cursors, only the cursor get updated, not the tables. when i try to loop and update, i get updates multiple times.
  i can't UPDATE WHERE -boolean function- (that accept the student_id and return if it should be updated). because the language won't allow it.</p>
  
  <p>any help will be appreciated
  cheers :-)</p>