Once the rows are sorted, the algorithm for joining the two tables is easy: the database server simply reads both sorted tables sequentially and merge all rows if they are matching.

一旦实现了对行的分类，连接两个表的算法就十分容易：数据库服务器仅仅连续地读取两个已分类表，并合并所有相匹配的行。

youdao

UPDATE is an INSERT, UPDATE, DELETE, or MERGE operation that may have input parameters and that returns an integer (number of affected rows).

更新是一个INSERT、UPDATE、DELETE或MERGE操作，可以有输入参数，返回一个整数(受影响的行数)。

youdao

You can use the --extratargetrows option with either of these three options: keep, delete, and merge to specify how to handle duplicate rows.

可以使用 --extratargetrows 选项，加上 keep、delete 和 merge 这三个选项中的一个，来规定如何处理重复行。

youdao

But when you need to optimize performance, you look at the queries you actually perform, then merge tables to create longer rows, and do away with joins wherever possible.

FORBES: What You Need to Know About NoSQL Databases