JOIN中的SQL语法错误(sql syntax error in JOIN)

 X的工作方式与任何网络程序的工作方式相同。 您有一个服务器（在这种情况下，X显示服务器）运行在特定的机器上，并且您有X客户端（如Firefox）尝试连接到该服务器以显示其信息。 
 
 通常（在“家”机器上），客户端和服务器在同一个盒子上运行，只有一个服务器，但X足够强大，这不需要发生。 它是从一开始构建的服务器/客户端分离内置的。 
 
 这样就可以让你做一些这样奇妙的事情，例如在地球上半部分登录到你的盒子（文本模式），告诉你，显示服务器是你当前正在使用的那个盒子，呃窗户突然出现在本地。 
 
 为了使客户端与用户交互，需要知道如何查找服务器。 有很多方法可以做到这一点。 许多客户端允许-display或--display选项来指定它： 
 
xeyes -display paxbox1.paxco.com:0.0
 
 如果没有明确给出显示，很多人会使用DISPLAY环境变量。 您可以像其他任何设置这个变量： 
 
DISPLAY=paxbox1.paxco.com:0.0; export DISPLAY # in .profile
export DISPLAY=paxbox1.paxco.com:0.0 # in your shell
DISPLAY=paxbox1.paxco.com:0.0 firefox & # for that command (shell permitting)
 
 DISPLAY变量的第一部分只是显示服务器机器的地址。 它遵循与任何其他IP地址相同的规则; 它可以是可解析的DNS名称（包括localhost ）或特定的IP地址（如192.168.10.55）。 
 
 第二部分是X特定的。 它给出X“显示”（X服务器）号码和屏幕号码的使用。 第一（显示编号）通常是指包含一个或多个屏幕但具有单个键盘和鼠标（即，一个输入流）的一组设备。 屏幕号通常给出该组内的特定屏幕。 
 
 一个例子是： 
 
+----------------------------------------+
|paxbox1.paxco.com|                      |
+-----------------+                      |
|                                        |
|  +----------+----+  +----------+----+  |
|  |Display :0|    |  |Display :1|    |  |
|  +----------+    |  +----------+    |  |
|  |               |  |               |  |
|  | +-----------+ |  |               |  |
|  | |Screen :0.0| |  |               |  |
|  | +-----------+ |  |               |  |
|  | +-----------+ |  |               |  |
|  | |Screen :0.1| |  |               |  |
|  | +-----------+ |  |               |  |
|  | +-----------+ |  | +-----------+ |  |
|  | |Screen :0.2| |  | |Screen :1.0| |  |
|  | +-----------+ |  | +-----------+ |  |
|  | +-----------+ |  | +-----------+ |  |
|  | |Screen :0.3| |  | |Screen :1.1| |  |
|  | +-----------+ |  | +-----------+ |  |
|  | +-----------+ |  | +-----------+ |  |
|  | | Keyboard  | |  | |  Keyboard | |  |
|  | +-----------+ |  | +-----------+ |  |
|  | +-----------+ |  | +-----------+ |  |
|  | |   Mouse   | |  | |   Mouse   | |  |
|  | +-----------+ |  | +-----------+ |  |
|  +---------------+  +---------------+  |
|                                        |
+----------------------------------------+
 
 在这里，您有一台带有两台显示服务器的单机（ paxbox1.paxco.com ）。 第一个有四个屏幕，第二个有两个屏幕。 可能性是： 
 
DISPLAY=paxbox1.paxco.com:0.0
DISPLAY=paxbox1.paxco.com:0.1
DISPLAY=paxbox1.paxco.com:0.2
DISPLAY=paxbox1.paxco.com:0.3
DISPLAY=paxbox1.paxco.com:1.0
DISPLAY=paxbox1.paxco.com:1.1
 
 取决于您希望实际的窗口出现在哪里，以及要使用的输入设备。 

The way that X works is the same as the way any network program works. You have a server of some description (in this case, the X display server) which runs on a specific machine, and you have X clients (like firefox) that try to connect to that server to get their information displayed.
 
Often (on "home" machines), the client and server run on the same box and there's only one server, but X is powerful enough that this doesn't need to happen. It was built with the server/client separation built in from the start.
 
This allows you to do such wondrous things such as log on to your box (in text mode) halfway around the planet, tell it that the display server is the box you're currently on and, voila, the windows suddenly start appearing locally.
 
In order for a client to interact with a user, it needs to know how to find the server. There are a number of ways to do this. Many clients allow the -display or --displayoption to specify it:
 
xeyes -display paxbox1.paxco.com:0.0
 
Many will use the DISPLAY environment variable if a display isn't specifically given. You can set this variable like any other:
 
DISPLAY=paxbox1.paxco.com:0.0; export DISPLAY # in .profile
export DISPLAY=paxbox1.paxco.com:0.0 # in your shell
DISPLAY=paxbox1.paxco.com:0.0 firefox & # for that command (shell permitting)
 
The first part of the DISPLAY variable is just the address of the display server machine. It follows the same rule as any other IP address; it can be a resolvable DNS name (including localhost) or a specific IP address (such as 192.168.10.55).
 
The second part is X-specific. It gives the X "display" (X server) number and screen number to use. The first (display number) generally refers to a group of devices containing one or more screens but with a single keyboard and mouse (i.e., one input stream). The screen number generally gives the specific screen within that group.
 
An example would be:
 
+----------------------------------------+
|paxbox1.paxco.com|                      |
+-----------------+                      |
|                                        |
|  +----------+----+  +----------+----+  |
|  |Display :0|    |  |Display :1|    |  |
|  +----------+    |  +----------+    |  |
|  |               |  |               |  |
|  | +-----------+ |  |               |  |
|  | |Screen :0.0| |  |               |  |
|  | +-----------+ |  |               |  |
|  | +-----------+ |  |               |  |
|  | |Screen :0.1| |  |               |  |
|  | +-----------+ |  |               |  |
|  | +-----------+ |  | +-----------+ |  |
|  | |Screen :0.2| |  | |Screen :1.0| |  |
|  | +-----------+ |  | +-----------+ |  |
|  | +-----------+ |  | +-----------+ |  |
|  | |Screen :0.3| |  | |Screen :1.1| |  |
|  | +-----------+ |  | +-----------+ |  |
|  | +-----------+ |  | +-----------+ |  |
|  | | Keyboard  | |  | |  Keyboard | |  |
|  | +-----------+ |  | +-----------+ |  |
|  | +-----------+ |  | +-----------+ |  |
|  | |   Mouse   | |  | |   Mouse   | |  |
|  | +-----------+ |  | +-----------+ |  |
|  +---------------+  +---------------+  |
|                                        |
+----------------------------------------+
 
Here you have a single machine (paxbox1.paxco.com) with two display servers. The first has four screens and the second has two. The possibilities are then:
 
DISPLAY=paxbox1.paxco.com:0.0
DISPLAY=paxbox1.paxco.com:0.1
DISPLAY=paxbox1.paxco.com:0.2
DISPLAY=paxbox1.paxco.com:0.3
DISPLAY=paxbox1.paxco.com:1.0
DISPLAY=paxbox1.paxco.com:1.1
 
depending on where you want your actual windows to appear and which input devices you want to use.