DDL (Data Definition Language 数据定义语言)

create table 创建表

alter table 修改表

drop table 删除表

truncate table 删除表中所有行

create index 创建索引

drop index 删除索引

当执行DDL语句时，在每一条语句前后，oracle都将提交当前的事务。如果用户使用insert命令将记录插入到数据库后，执行了一条DDL语句(如create table)，此时来自insert命令的数据将被提交到数据库。当DDL语句执行完成时，DDL语句会被自动提交，不能回滚。

DML (Data Manipulation Language 数据操作语言)

insert 将记录插入到数据库

update 修改数据库的记录

delete 删除数据库的记录

当执行DML命令如果没有提交，将不会被其他会话看到。除非在DML命令之后执行了DDL命令或DCL命令，或用户退出会话，或终止实例，此时系统会自动发出commit命令，使未提交的DML命令提交。

Table 14.8 Online DDL Support for Index Operations

OperationIn PlaceRebuilds TablePermits Concurrent DMLOnly Modifies Metadata

Creating or adding a secondary index

Yes

No

Yes

No

Dropping an index

Yes

No

Yes

Yes

Adding aFULLTEXTindex

Yes*

No*

No

No

Table 14.9 Online DDL Support for Primary Key Operations

OperationIn PlaceRebuilds TablePermits Concurrent DMLOnly Modifies Metadata

Adding a primary key

Yes*

Yes*

Yes

No

Dropping a primary key

No

Yes

No

No

Dropping a primary key and adding another

Yes

Yes

Yes

No

Table 14.10 Online DDL Support for Column Operations

OperationIn PlaceRebuilds TablePermits Concurrent DMLOnly Modifies Metadata

Adding a column

Yes

Yes

Yes*

No

Dropping a column

Yes

Yes

Yes

No

Renaming a column

Yes

No

Yes*

Yes

Reordering columns

Yes

Yes

Yes

No

Setting a column default value

Yes

No

Yes

Yes

Changing the column data type

No

Yes

No

No

Dropping the column default value

Yes

No

Yes

Yes

Changing the auto-increment value

Yes

No

Yes

No*

Making a columnNULL

Yes

Yes*

Yes

No

Making a columnNOT NULL

Yes*

Yes*

Yes

No

Table 14.11 Online DDL Support for Foreign Key Operations

OperationIn PlaceRebuilds TablePermits Concurrent DMLOnly Modifies Metadata

Adding a foreign key constraint

Yes*

No

Yes

Yes

Dropping a foreign key constraint

Yes

No

Yes

Yes

Table 14.12 Online DDL Support for Table Operations

OperationIn PlaceRebuilds TablePermits Concurrent DMLOnly Modifies Metadata

Changing theROW_FORMAT

Yes

Yes

Yes

No

Changing theKEY_BLOCK_SIZE

Yes

Yes

Yes

No

Setting persistent table statistics

Yes

No

Yes

Yes

Specifying a character set

Yes*

Yes*

No

No

Converting a character set

No

Yes

No

No

Optimizing a table

Yes*

Yes

Yes

No

Rebuilding with theFORCEoption

Yes*

Yes

Yes

No

Performing a null rebuild

Yes*

Yes

Yes

No