Many DDL operations on tables and indexes (CREATE, ALTER, and DROP statements) can be performed online. 表和索引上的许多DDL操作（CREATE、ALTER和DROP语句）都可以在线执行。See Section 15.12, “InnoDB and Online DDL” for details.详见第15.12节，“InnoDB和在线DDL”。

Online DDL support for adding secondary indexes means that you can generally speed up the process of creating and loading a table and associated indexes by creating the table without secondary indexes, then adding secondary indexes after the data is loaded.对添加辅助索引的在线DDL支持意味着您通常可以通过创建不带辅助索引的表，然后在加载数据后添加辅助索引来加快创建和加载表及其关联索引的过程。

Use TRUNCATE TABLE to empty a table, not DELETE FROM tbl_name. Foreign key constraints can make a TRUNCATE statement work like a regular DELETE statement, in which case a sequence of commands like DROP TABLE and CREATE TABLE might be fastest.

Because the primary key is integral to the storage layout of each InnoDB table, and changing the definition of the primary key involves reorganizing the whole table, always set up the primary key as part of the CREATE TABLE statement, and plan ahead so that you do not need to ALTER or DROP the primary key afterward.