As a database developer, you usually join the customer table to the contact table and treat the customer as the main table.
作为数据库开发人员，您通常将客户表与联系方式表连接，并将客户表视作主表。
With side tables, DB2 first performs an index lookup on the side table and then joins the corresponding row with the main table that contains the CLOBs.
在使用索引表的情况下，DB 2首先对索引表执行索引查找，然后将对应的行和包含CLOB的主表相结合。
So to find the row that satisfies the predicate in the select statement, the optimizer has to lock, read in, and compare all the rows in the main table with the value supplied in the predicate.
因此要找到满足select语句中谓词的行，这个优化器必须将主表中的所有行上锁、读取它们的值并与谓词中提供的值进行比较。
Updates made to the main table result in actions that push out the previous values of data to the history tables. This is either done through triggers or by the applications themselves.
在更新主表的时候会把旧数据推入历史表中，这个过程一般是通过触发器或由应用程序自己来完成。
Updates made to the main table result in actions that push out the previous values of data to the history tables. This is either done through triggers or by the applications themselves.
在更新主表的时候会把旧数据推入历史表中，这个过程一般是通过触发器或由应用程序自己来完成。
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