MySQL5.6的版本之后支持了在线DDL,这对于DBA来说是个福音，但是MySQL5.6、5.7和当前的最新版本8.0在各种DDL中的情况不太一样，根据MySQL官方网站的说明整理一份在线DDL的对比情况，具体如下：
| Type | Operation | Instant | In Place | Rebuilds Table | Permits Concurrent DML | Only Modifies Metadata | ||||||||||
| 5.6 | 5.7 | 8.0 | 5.6 | 5.7 | 8.0 | 5.6 | 5.7 | 8.0 | 5.6 | 5.7 | 8.0 | 5.6 | 5.7 | 8.0 | ||
| Index Operations | Creating or adding a secondary index | No | Yes | Yes | Yes | No | No | No | Yes | Yes | Yes | No | No | No | ||
| Dropping an index | No | Yes | Yes | Yes | No | No | No | Yes | Yes | Yes | Yes | Yes | Yes | |||
| Renaming an index | No | Yes | Yes | No | No | Yes | Yes | Yes | Yes | |||||||
| Adding a FULLTEXT index | No | Yes* | Yes* | Yes* | No* | No* | No* | No | No | No | No | No | No | |||
| Adding a SPATIAL index | No | Yes | Yes | No | No | No | No | No | No | |||||||
| Changing the index type | Yes | Yes | Yes | Yes | No | No | No | Yes | Yes | Yes | Yes | Yes | Yes | |||
| Type | Operation | Instant | In Place | Rebuilds Table | Permits Concurrent DML | Only Modifies Metadata | ||||||||||
| 5.6 | 5.7 | 8.0 | 5.6 | 5.7 | 8.0 | 5.6 | 5.7 | 8.0 | 5.6 | 5.7 | 8.0 | 5.6 | 5.7 | 8.0 | ||
| Primary Key Operations | Adding a primary key | No | Yes* | Yes* | Yes* | Yes* | Yes* | Yes* | Yes | Yes | Yes | No | No | No | ||
| Dropping a primary key | No | No | No | No | Yes | Yes | Yes | No | No | No | No | No | No | |||
| Dropping a primary key and adding another | No | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | No | No | No | |||
| Type | Operation | Instant | In Place | Rebuilds Table | Permits Concurrent DML | Only Modifies Metadata | ||||||||||
| 5.6 | 5.7 | 8.0 | 5.6 | 5.7 | 8.0 | 5.6 | 5.7 | 8.0 | 5.6 | 5.7 | 8.0 | 5.6 | 5.7 | 8.0 | ||
| Column Operations | Adding a column | Yes* | Yes | Yes | Yes | Yes | Yes | Yes | Yes* | Yes* | Yes* | No | No | No | ||
| Dropping a column | No | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | No | No | No | |||
| Renaming a column | No | Yes | Yes | Yes | No | No | No | Yes* | Yes* | Yes* | Yes | Yes | Yes | |||
| Reordering columns | No | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | No | No | No | |||
| Setting a column default value | Yes | Yes | Yes | Yes | No | No | No | Yes | Yes | Yes | Yes | Yes | Yes | |||
| Changing the column data type | No | No | No | No | Yes | Yes | Yes | No | No | No | No | No | No | |||
| Extending VARCHAR column size | No | Yes | Yes | No | No | Yes | Yes | Yes | Yes | |||||||
| Dropping the column default value | Yes | Yes | Yes | Yes | No | No | No | Yes | Yes | Yes | Yes | Yes | Yes | |||
| Changing the auto-increment value | No | Yes | Yes | Yes | No | No | No | Yes | Yes | Yes | No* | No* | No* | |||
| Making a column NULL | No | Yes | Yes | Yes | Yes* | Yes* | Yes* | Yes | Yes | Yes | No | No | No | |||
| Making a column NOT NULL | No | Yes* | Yes* | Yes* | Yes* | Yes* | Yes* | Yes | Yes | Yes | No | No | No | |||
| Modifying the definition of an ENUM or SET column | Yes | Yes | Yes | Yes | No | No | No | Yes | Yes | Yes | Yes | Yes | Yes | |||
| Type | Operation | Instant | In Place | Rebuilds Table | Permits Concurrent DML | Only Modifies Metadata | ||||||||||
| 5.6 | 5.7 | 8.0 | 5.6 | 5.7 | 8.0 | 5.6 | 5.7 | 8.0 | 5.6 | 5.7 | 8.0 | 5.6 | 5.7 | 8.0 | ||
| Generated Column Operations | Adding a STORED column | No | No | No | Yes | Yes | No | No | No | No | ||||||
| Modifying STORED column order | No | No | No | Yes | Yes | No | No | No | No | |||||||
| Dropping a STORED column | No | Yes | Yes | Yes | Yes | Yes | Yes | No | No | |||||||
| Adding a VIRTUAL column | Yes | Yes | Yes | No | No | Yes | Yes | Yes | Yes | |||||||
| Modifying VIRTUAL column order | No | No | No | Yes | Yes | No | No | No | No | |||||||
| Dropping a VIRTUALcolumn | Yes | Yes | Yes | No | No | Yes | Yes | Yes | Yes | |||||||
| Type | Operation | Instant | In Place | Rebuilds Table | Permits Concurrent DML | Only Modifies Metadata | ||||||||||
| 5.6 | 5.7 | 8.0 | 5.6 | 5.7 | 8.0 | 5.6 | 5.7 | 8.0 | 5.6 | 5.7 | 8.0 | 5.6 | 5.7 | 8.0 | ||
| Foreign Key Operations | Adding a foreign key constraint | No | Yes* | Yes* | Yes* | No | No | No | Yes | Yes | Yes | Yes | Yes | Yes | ||
| Dropping a foreign key constraint | No | Yes | Yes | Yes | No | No | No | Yes | Yes | Yes | Yes | Yes | Yes | |||
| Type | Operation | Instant | In Place | Rebuilds Table | Permits Concurrent DML | Only Modifies Metadata | ||||||||||
| 5.6 | 5.7 | 8.0 | 5.6 | 5.7 | 8.0 | 5.6 | 5.7 | 8.0 | 5.6 | 5.7 | 8.0 | 5.6 | 5.7 | 8.0 | ||
| Table Operations | Changing the ROW_FORMAT | No | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | No | No | No | ||
| Changing the KEY_BLOCK_SIZE | No | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | No | No | No | |||
| Setting persistent table statistics | No | Yes | Yes | Yes | No | No | No | Yes | Yes | Yes | Yes | Yes | Yes | |||
| Specifying a character set | No | Yes | Yes | Yes | Yes* | Yes* | Yes* | No | No | No | No | No | No | |||
| Converting a character set | No | No | No | No | Yes | Yes* | Yes* | No | No | No | No | No | No | |||
| Optimizing a table | No | Yes* | Yes* | Yes* | Yes | Yes | Yes | Yes | Yes | Yes | No | No | No | |||
| Enabling or disabling table encryption | No | No | No | Yes | Yes | No | No | Yes | Yes | |||||||
| Rebuilding with the FORCEoption | No | Yes* | Yes* | Yes* | Yes | Yes | Yes | Yes | Yes | Yes | No | No | No | |||
| Performing a null rebuild | No | Yes* | Yes* | Yes* | Yes | Yes | Yes | Yes | Yes | Yes | No | No | No | |||
| Renaming a table | Yes | Yes | Yes | Yes | No | No | No | Yes | Yes | Yes | Yes | Yes | Yes | |||