lightdb22.3-新增支持oracle语法(modify column&drop primary key)

Posted 2022-10-16 紫无之紫

lightdb 22.3 - 新增支持oracle 语法（modify column&drop primary key）

在LightDB 22.3 版本中新增了oracle语法的支持：

• 对alter table modify column语法的部分支持，下面会列出具体支持哪些， 哪些不支持。
• 对 alter table drop primary key 的支持，可以不通过约束名直接删除主键

modify column

修改字段属性，目前支持如下用法：

1. 修改字段类型, oracle 没有USING expression, lightdb用于指定cast
MODIFY column_name data_type [ USING expression ]

2. 修改字段默认值
MODIFY column_name DEFAULT expression 

3. 修改字段 是否可为null
MODIFY column_name  NOT NULL | NULL  [ENABLE]

4. 修改字段 IDENTITY
MODIFY column_name GENERATED  ALWAYS | BY DEFAULT  AS IDENTITY [ ( sequence_options ) ]
MODIFY column_name DROP IDENTITY
    MODIFY column_name CONSTRAINT constraint_name  NOT NULL | NULL  [ENABLE]
    
5. 修改字段增加约束
-- unique
MODIFY column_name CONSTRAINT constraint_name UNIQUE [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]
-- PRIMARY KEY
MODIFY column_name CONSTRAINT constraint_name PRIMARY KEY [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]
-- REFERENCES
MODIFY column_name CONSTRAINT constraint_name REFERENCES reftable [ ( refcolumn ) ] 
    [ MATCH FULL | MATCH PARTIAL | MATCH SIMPLE ] [ ON DELETE referential_action ] [ ON UPDATE referential_action ] [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]
-- CHECK 目前不检验实际字段是否一致
MODIFY column_name CONSTRAINT constraint_name CHECK '(' a_expr ')' [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]

不支持用法

• modify_col_properties:

  • encrypt/decrypt

  • LOB_storage_clause

  • alter_XMLSchema_clause

  • default on null

• modify_virtcol_properties

• modify_col_visibility

• modify_col_substitutable

drop primary key

语法：

alter table table_name drop priamry key;