DB常用操作

增加列：alter table tableName add columnName number(10);

增加列并设置默认值: alter table tableName add columnName number(10) default 0; 

删除列：ALTER Table tableName DROP column columnName;

将某列数值置为null：alter table tableName modify columnName null;

修改列的类型：alter table tableName modify columnName number(12,3);

重命名列名称: alter table tableName rename column oldColumn to newColumn;

设置Primary key ：ALTER TABLE tableName ADD CONSTRAINT 主键名
      PRIMARY KEY (columnName)

更改主键，并设置index,tablespace :
alter table tableName
    add constraint 主键名 primary key (columnName1, columnName2)
    using index

tablespace USERS
  pctfree 10
  initrans 2
  maxtrans 255
  storage
  (
    initial 64K
    minextents 1
    maxextents unlimited
  );

创建table并添加注释:
create table table1                  
(                                          
    name varchar(20) not null             
); 

  tablespace USERS
  pctfree 10
  initrans 1
  maxtrans 255
  storage
  (
    initial 64K
    minextents 1
    maxextents unlimited
  );                                            
  comment on column table1.name
    is '名称';

创建序列：

   create sequence  sequenceName
minvalue 1                         
maxvalue 999999999999999999999999999
start with 241                     
increment by 1                     
cache 20; 

创建同义词：

    prompt
    prompt Creating synonym tableName
    prompt =======================================
    prompt
       create or replace synonym tableName  for tableName@DBLinkName
    spool off

删除表（含表结构）：drop table tableName

删除表数据：delete from tableName

更新列值:  update tableName set columnName = columnValue;

####MySqL

从模板表创建表：create table if not exists like old_table_name;

创建表：create table if not exists table_name

删除表：drop table if exists table_name