我有实体Parent和Child与单边关系Child n -> 1 Parent。换句话说，Parent不了解其子女。
如何编写一个JPQL查询，该查询会选择Parent的所有Child个实例，而select all parents which are not referred to by children who are younger than 8 years的特定子集不会引用这些实例符合某个谓词？
实施例：
from __future__ import division
from Tkinter import *
import math
main = Tk()
main.title("Calculator")
main.geometry("375x550")
entry = Text(main)
entry.configure(width=17,height=1)
entry.place(x=13, y=5)
entry.config(font=("Courier", 25))
def oneButtonFunction(event):
entry.insert(END, '1')
def twoButtonFunction(event):
entry.insert(END, '2')
def threeButtonFunction(event):
entry.insert(END, '3')
def fourButtonFunction(event):
entry.insert(END, '4')
def fiveButtonFunction(event):
entry.insert(END, '5')
def sixButtonFunction(event):
entry.insert(END, '6')
def sevenButtonFunction(event):
entry.insert(END, '7')
def eightButtonFunction(event):
entry.insert(END, '8')
def nineButtonFunction(event):
entry.insert(END, '9')
def zeroButtonFunction(event):
entry.insert(END, '0')
def addButtonFunction(event):
entry.insert(END, '+')
def subButtonFunction(event):
entry.insert(END, '-')
def multButtonFunction(event):
entry.insert(END, '*')
def divButtonFunction(event):
entry.insert(END, '/')
def decimalButtonFunction(event):
entry.insert(END, '.')
def equalButtonFunction(event):
x = entry.get("1.0", "end-1c")
entry.delete("1.0", END)
entry.insert(END, eval(x))#causes error for trig function
def clearButtonFunction(event):
entry.delete("1.0", END)
def parentheses1ButtonFuction(event):
entry.insert(END, '(')
def parentheses2ButtonFuction(event):
entry.insert(END, ')')
def trigButtonFunction(event):
sinButton.place(x=280, y=50)
cosButton.place(x=280, y=150)
tanButton.place(x=280, y=250)
backButton.place(x=280, y=450)
def sinButtonFunction(event):
entry.insert(END, 'sin(')
def cosButtonFunction(event):
entry.insert(END, 'cos(')
def tanButtonFunction(event):
entry.insert(END, 'tan(')
def backButtonFunction(event):
sinButton.place_forget()
cosButton.place_forget()
tanButton.place_forget()
backButton.place_forget()
oneButton = Button(main, text="1", width=10, height=5)
oneButton.place(x=10, y=50)
oneButton.bind('<Button-1>', oneButtonFunction)
twoButton = Button(main, text="2", width=10, height=5)
twoButton.place(x=100, y=50)
twoButton.bind('<Button-1>', twoButtonFunction)
threeButton = Button(main, text="3", width=10, height=5)
threeButton.place(x=190, y=50)
threeButton.bind('<Button-1>', threeButtonFunction)
fourButton = Button(main, text="4", width=10, height=5)
fourButton.place(x=10, y=150)
fourButton.bind('<Button-1>', fourButtonFunction)
fiveButton = Button(main, text="5", width=10, height=5)
fiveButton.place(x=100, y=150)
fiveButton.bind('<Button-1>', fiveButtonFunction)
sixButton = Button(main, text="6", width=10, height=5)
sixButton.place(x=190, y=150)
sixButton.bind('<Button-1>', sixButtonFunction)
sevenButton = Button(main, text="7", width=10, height=5)
sevenButton.place(x=10, y=250)
sevenButton.bind('<Button-1>', sevenButtonFunction)
eightButton = Button(main, text="8", width=10, height=5)
eightButton.place(x=100, y=250)
eightButton.bind('<Button-1>', eightButtonFunction)
nineButton = Button(main, text="9", width=10, height=5)
nineButton.place(x=190, y=250)
nineButton.bind('<Button-1>', nineButtonFunction)
zeroButton = Button(main, text="0", width=10, height=5)
zeroButton.place(x=100, y=350)
zeroButton.bind('<Button-1>', zeroButtonFunction)
decimalButton = Button(main, text=".", width=10, height=5)
decimalButton.place(x=10, y=350)
decimalButton.bind('<Button-1>', decimalButtonFunction)
equalButton = Button(main, text="=", width=10, height=5)
equalButton.place(x=190, y=350)
equalButton.bind('<Button-1>', equalButtonFunction)
addButton = Button(main, text="+", width=10, height=5)
addButton.place(x=280, y=50)
addButton.bind('<Button-1>', addButtonFunction)
subButton = Button(main, text="-", width=10, height=5)
subButton.place(x=280, y=150)
subButton.bind('<Button-1>', subButtonFunction)
multButton = Button(main, text="X", width=10, height=5)
multButton.place(x=280, y=250)
multButton.bind('<Button-1>', multButtonFunction)
divButton = Button(main, text="/", width=10, height=5)
divButton.place(x=280, y=350)
divButton.bind('<Button-1>', divButtonFunction)
clearButton = Button(main, text="Clear", width=10, height=5)
clearButton.place(x=10, y=450)
clearButton.bind('<Button-1>', clearButtonFunction)
parentheses1Button = Button(main, text="(", width=10, height=5)
parentheses1Button.place(x=100, y=450)
parentheses1Button.bind('<Button-1>', parentheses1ButtonFuction)
parentheses2Button = Button(main, text=")", width=10, height=5)
parentheses2Button.place(x=190, y=450)
parentheses2Button.bind('<Button-1>', parentheses2ButtonFuction)
trigButton = Button(main, text="Trig", width=10, height=5)
trigButton.place(x=280, y=450)
trigButton.bind('<Button-1>', trigButtonFunction)
sinButton = Button(main, text="Sin", width=10, height=5)
sinButton.bind('<Button-1>', sinButtonFunction)
cosButton = Button(main, text="Cos", width=10, height=5)
cosButton.bind('<Button-1>', cosButtonFunction)
tanButton = Button(main, text="Tan", width=10, height=5)
tanButton.bind('<Button-1>', tanButtonFunction)
backButton = Button(main, text="Back", width=10, height=5)
backButton.bind('<Button-1>', backButtonFunction)
main.mainloop()
答案 0 :(得分：0)
您可以尝试父/子关系的LEFT OUTER JOIN，例如：
SELECT c, p.name FROM Country c LEFT OUTER JOIN c.capital p
如果空值存在问题，可以通过添加类似以下内容来删除它们：
... WHERE p.id IS NOT NULL
有关详细说明，请参阅本指南：http://www.objectdb.com/java/jpa/query/jpql/from#LEFT_OUTER_JOIN_
如果父级不了解子级，则可以通过使用子查询来过滤父级来实现类似的结果，例如：
SELECT e.parent_id
FROM ParentEntity e
WHERE e.parent_id NOT IN (
SELECT c.parent_id FROM ChildEntity c) ...