All Tracks Problem

Little Shino and Unique Students
Tag(s):

Easy, 簡単

Problem
Editorial
Analytics

University of Byteland introduce a new way to count the attendance of students. They provide all the students with an unique ID card. Daily each student have to swipe their ID card in a machine to attend the class.

University have the data of last one month stored in a table Attendance. They asked you find out how many unique students attended any class in last one week including today's attendance.

NOTE: Today's date is 2016-12-17.

The output table should be ordered by Student names in lexicographically increasing order.

Input Format:

Table : Attendance

Field Type
Student text
DateColumn date

Output Format:

Field Type
Student text

Sample Input:

Sample Attendance Table:

Student DateColumn
b 2016-12-16
ac 2016-12-10
b 2016-12-17
a 2016-12-10
ac 2016-12-11

Sample Output:

Student
ac
b
Time Limit: 5 sec(s) for each input file.
Memory Limit: 256 MB
Source Limit: 1024 KB
Marking Scheme: Marks are awarded when all the testcases pass.
Allowed Languages: MySQL, PostgreSQL, MSSQL, Oracle Database

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