带有联接的Sql更新失败

我有这个查询，返回一个错误，显示"您的SQL语法有错误；请查看与您的MySQL服务器版本相对应的手册，在第1行的'FROM Sales JOIN Sales ON Inventory.saleID=Sales.ID JOIN Customers ON Sales.custo'附近找到正确的语法

这是我的问题。我知道我没有使用别名，所以它看起来很难看，但语法似乎是正确的，并且我传入的变量不为空，我已经将它们回显了。

 $sql = "UPDATE Sales SET salequantity='$takeCount' 
       FROM `Sales` 
       JOIN Sales ON Inventory.saleID=Sales.ID 
       JOIN Customers ON Sales.customerID=Customers.ID 
       JOIN Products ON Inventory.productID = Products.ID 
      JOIN Categories ON Products.categoryID=Categories.ID 
      WHERE Customers.ID='$customersID' AND Products.ID='$id'";

这是我的模式

CREATE TABLE Categories
(
ID int NOT NULL auto_increment,
type varchar(255),
description varchar(255),
PRIMARY KEY (ID)
);
CREATE TABLE Products
(
ID int NOT NULL auto_increment,
categoryID int,
customerID int,
name varchar(255),
description varchar(255),
price float(10),
quantity int(10),
PRIMARY KEY (ID),
FOREIGN KEY (categoryID) REFERENCES Categories(ID)
);
CREATE TABLE Customers
(
ID int NOT NULL auto_increment,
productID int,
name varchar(255),
street varchar(255),
city varchar(255),
state varchar(255),
zip int(8),
username varchar(255),
password varchar(255),
confirm_password varchar(255),
phone varchar(255),
PRIMARY KEY (ID),
);
CREATE TABLE Sales
(
ID int NOT NULL auto_increment,
customerID int,
amount float(15),
salequantity int(10),
PRIMARY KEY (ID),
FOREIGN KEY (customerID) REFERENCES Customers(ID)
);
CREATE TABLE Inventory
(
productID int,
saleID int,
FOREIGN KEY (productID) REFERENCES Products(ID),
FOREIGN KEY (saleID) REFERENCES Sales(ID)
);

这是最后一个查询。只要这个简单的工作。

UPDATE Sales  INNER JOIN Sales ON Inventory.saleID=Sales.ID SET salequantity=2 where Sales.customerID=1 AND Inventory.productID=1;

从第一条注释运行了查询，但也失败了。

UPDATE Sales SET salequantity=5 FROM Sales JOIN Inventory ON Inventory.saleID=Sales.ID JOIN Customers ON Sales.customerID=Customers.ID JOIN Products ON Inventory.productID = Products.ID JOIN Categories ON Products.categoryID=Categories.ID where Customers.ID=1 AND Products.ID=1;

解决方案聚合函数这是完美的

$customerProducts = mysql_query("select Products.ID, Products.name, Products.description, Products.quantity,Products.price, Categories.type, Sales.ID, Sales.customerID, Sales.amount, Sales.salequantity, Inventory.productID, Inventory.saleID, Customers.ID, Customers.productID, COUNT(Products.name) AS productsCount from(((( Inventory INNER JOIN Sales ON Inventory.saleID=Sales.ID) JOIN Customers ON Sales.customerID=Customers.ID) JOIN Products ON Inventory.productID = Products.ID) JOIN Categories ON Products.categoryID=Categories.ID) where Customers.ID ='$customersID' GROUP BY Products.name");