Python 将不同表中的多条记录合并为一个字符串

我试图使用studentID从一个表中获取他们的名字和姓氏，然后使用HomeworkID获取他们其中一个作业的结果，并使用tkinter将结果显示在listbox小部件中。当然，在它被显示之前，我首先需要能够获得数据。 这就是我迄今为止所做的：

 def viewresults (self, sethw):

        print (self.Homework_To_Set.get())
        #resultslist = []
        conn = sqlite3.connect('MyComputerScience.db')
        c = conn.cursor()
        homeworkID = c.execute("SELECT HWID FROM HomeworkInfo WHERE HomeworkName = ?", (self.Homework_To_Set.get(), )).fetchone()
        studentsnamecheck = c.execute("SELECT StudentID FROM HomeworkSet WHERE  HWID = ?", ((homeworkID[0], ))).fetchall()
        if len(studentsnamecheck) == 0:
            self.View_Results.insert(END, "No one has completed this homework!")
        else:
            for x in studentsnamecheck:
                c.execute("SELECT FName || ' ' || SName FROM users WHERE UserID = ?", (str(x), ))
                res1 = (c.fetchall())
                for i in (studentsnamecheck):
                    result_collect = c.execute("SELECT Results FROM HomeworkSet WHERE StudentID = ? AND HWID = ?", ((str(i)), self.Homework_To_Set.get() ))

                var_insert_results = ((res1), (result_collect))
                self.View_Results.insert(END, str(var_insert_results))

这是电流输出：

([], <sqlite3.Cursor object at 0x000001F40E1809D0>)
([], <sqlite3.Cursor object at 0x000001F40E1809D0>)
([], <sqlite3.Cursor object at 0x000001F40E1809D0>)
([], <sqlite3.Cursor object at 0x000001F40E1809D0>)
([], <sqlite3.Cursor object at 0x000001F40E1809D0>)
([], <sqlite3.Cursor object at 0x000001F40E1809D0>)
([], <sqlite3.Cursor object at 0x000001F40E1809D0>)

---

您的代码中有几个问题：

c.execute("SELECT FName || ' ' || SName FROM users WHERE UserID = ?", (str(x), ))
res1 = (c.fetchall())
for i in (studentsnamecheck):
    result_collect = c.execute("SELECT Results FROM HomeworkSet WHERE StudentID = ? AND HWID = ?",
                               ((str(i)), self.Homework_To_Set.get() ))

• users

  表中没有

  UserID

  字段；它可能是

  用户名

• str（x）

  应该是

  x[0]

• 应该循环通过

  res1

  而不是

  studentsnamecheck

• str（i）

  应该是

  x[0]

• self.journalization\u To\u Set.get（）

  应该是

  homeworkind[0]

因此，代码应该是：

def viewresults(self, sethw):
    print(self.Homework_To_Set.get())
    conn = sqlite3.connect('MyComputerScience.db')
    c = conn.cursor()
    homeworkID = c.execute("SELECT HWID FROM HomeworkInfo WHERE HomeworkName = ?",
                           (self.Homework_To_Set.get(),)).fetchone()
    studentsnamecheck = c.execute("SELECT StudentID FROM HomeworkSet WHERE HWID = ?",
                                  (homeworkID[0],)).fetchall()
    if len(studentsnamecheck) == 0:
        self.View_Results.insert(END, "No one has completed this homework!")
    else:
        for x in studentsnamecheck:
            c.execute("SELECT FName||' '||SName FROM users WHERE username = ?", (x[0],))
            res1 = c.fetchall()
            for i in res1:
                results = c.execute("SELECT Results FROM HomeworkSet WHERE StudentID = ? AND HWID = ?",
                                    (x[0], homeworkID[0])).fetchone()
                self.View_Results.insert(END, '%-30s  %s'%(i[0], results[0]))

但是，您可以将

SELECT

语句组合到一个查询中：

def viewresults(self, sethw):
    conn = sqlite3.connect('MyComputerScience.db')
    c = conn.cursor()
    sql = """
        SELECT SName||' '||FName, Results
        FROM HomeworkSet, HomeworkInfo, users
        WHERE HomeworkInfo.HomeworkName = ?
          AND HomeworkInfo.HWID = HomeworkSet.HWID
          AND HomeworkSet.StudentID = users.username
    """
    c.execute(sql, (self.Homework_To_Set.get(),))
    for result in c:
        self.View_Results.insert(END, '%-30s  %s'%result)

---

“当前输出：……您可以使用SQL JOIN组合三个SELECT语句，因此可以使用一个for循环遍历结果。

def viewresults(self, sethw):
    conn = sqlite3.connect('MyComputerScience.db')
    c = conn.cursor()
    sql = """
        SELECT SName||' '||FName, Results
        FROM HomeworkSet, HomeworkInfo, users
        WHERE HomeworkInfo.HomeworkName = ?
          AND HomeworkInfo.HWID = HomeworkSet.HWID
          AND HomeworkSet.StudentID = users.username
    """
    c.execute(sql, (self.Homework_To_Set.get(),))
    for result in c:
        self.View_Results.insert(END, '%-30s  %s'%result)