So the line is the primary side and the secondary side.

所以，这条线是主要的一面,还有第二面。

youdao

The primary key side of a one-to-one relationship is denoted by a key symbol.

一对一关系的主键方由键符号表示。

youdao

The primary key side of a one-to-one relationship is denoted by a key symbol.

一对一关系的主键方由键符号表示。

youdao