第一张table

$sql = "CREATE TABLE if not exists mainInfo (
sku varchar(20) primary key not null,
name varchar(20) not null,
price int(30) not null,
type int(2) not null
)";

第二张table

$sql="CREATE TABLE if NOT EXISTS properties (
size int(9),
bWeight int(9),
fHeight int(9),
fWeight int(9),
fLenght int(9),
sku varchar(20) not null,
CONSTRAINT FK_mainInfoProperties FOREIGN KEY (sku) REFERENCES mainInfo(sku)
)";

内部联接表

$sql = "CREATE TABLE if NOT EXISTS allInfo (
        sku varchar(20) primary key not null,
        name varchar(20) not null,
        price int(30) not null,
        type int(2) not null,
        size int(9),
        bWeight int(9),
        fHeight int(9),
        fWeight int(9),
        fLenght int(9)
         )";

       $sql = "INSERT INTO allInfo (sku, name, price, type, size, bWeight, 
       fHeight, fWeight, fLenght)
        SELECT mainInfo.sku, name, price, type, size, bWeight, fHeight, 
       fWeight, fLenght
        FROM mainInfo INNER JOIN properties
        ON mainInfo.sku = properties.sku";

我第一次使用这段代码时，它是工作的，但是当我向第一个和第二个表中添加新行时，内部联接表不会更新它，给我键'primary'的重复条目。我如何更新这个表，添加新行，但保留已经存在的行不变？