它们是由细微的藻类、生物和细菌组成的漂流汤，甚至算不上一组物种，但是却连接起了整个分类王国。
A drifting soup of microscopic algae, creatures and bacteria, they are not even one group of species but bridge entire taxonomic kingdoms.
因为该方法在进行表连接之前，必须将所有的连接表分类，所以其成本通常极其高。
Because this method has to sort all joining tables before they join, the costs are usually pretty high.
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。
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.
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