如何修复以下MYSQL语句？

Question

List the number of Judges graduated from each law school. The tables are Presidents , Judges , and Appoints . Judges has columns JName , DateOfBirth , LawSchool . I have tried the following statement and am running into an error I am not sure I understand completely:

SELECT jname, COUNT(jname)
FROM Judges J1, Judges J2
WHERE J1.LawSchool = J2.LawSchool AND J1.Jname != J2.Jname;

The error is: ERROR 1052: Column 'jname' in field list is ambiguous .

Answer 1

The field jname exist in more then one table that you are selecting data from (Judges J1 & Judges J2). You have to specify which table you want this data from. But, according to your task, I think the right way to do this is:

SELECT LawSchool, COUNT(*)
FROM Judges
Group By LawSchool