在 Oracle 中创建视图时更改列精度答案

【问题标题】：Changing the column precision while creating a view in Oracle在 Oracle 中创建视图时更改列精度
【发布时间】：2012-05-11 18:51:06
【问题描述】：

 CREATE OR REPLACE VIEW USER_AUD_VIEW ("AUDIT_ID", "USER_ID", "TABLE_NAME_TXT",      "COLUMN_NAME_TXT", "OLD_VALUE_TXT", "NEW_VALUE_TXT", "AUDIT_LAST_UPDATED_DT", "AUDIT_UPDATED_USER_ID", "EVALUATOR_ID", "PRODUCT_ID")
 AS
   SELECT acm.audit_id,
GET_TOKEN(GET_TOKEN(acm.PRIMARY_KEY_VALUES,1,','),2,':') AS user_id,
acm.table_name_txt,
acm.column_name_txt,
CASE
  WHEN UPPER(acm.column_name_txt) = 'PASSWORD_TXT'
  THEN '******'
  ELSE acm.old_value_txt
END AS old_value_txt,
CASE
  WHEN UPPER(acm.column_name_txt) = 'PASSWORD_TXT'
  THEN '******'
  ELSE acm.new_value_txt
END AS new_value_txt,
acm.audit_last_updated_dt,
CASE
  WHEN UPPER(acm.audit_updated_user_id) = 'UNKNOWN'
  THEN acm.audit_updated_user_id
  ELSE (users.user_id
    || ' ('
    || DECODE(users.last_name_txt, NULL,' ' , users.last_name_txt)
    || ', '
    || DECODE(users.first_name_txt, NULL,'' , users.first_name_txt)
    || ')' )
END    
AS audit_uupdated_user_id,
acm.evaluator_id,
TO_NUMBER(GET_TOKEN(GET_TOKEN(acm.PRIMARY_KEY_VALUES,2,','),2,':')) AS product_id

   FROM audit_config_maintenance acm,
users
   WHERE acm.table_name_txt             in ('USERS','XREF_USER_PRODUCT')
   AND UPPER(acm.audit_updated_user_id) = UPPER(users.user_id)
   AND acm.primary_key_values is not null

在创建上述视图时，get_token() 函数将列类型设为 varchar2(4000)。如何更改命令以使该字段成为 varchar2(64) ？

【问题讨论】：

标签： oracle view precision varchar

【解决方案1】：

你可以使用CAST函数，即CAST( GET_TOKEN(GET_TOKEN(acm.PRIMARY_KEY_VALUES,1,','),2,':') AS VARCHAR2(64)

如果你创建一个函数

SQL> create or replace function my_function
  2    return varchar2
  3  is
  4  begin
  5    return 'foo';
  6  end;
  7  /

Function created.

然后选择此函数的简单视图将具有VARCHAR2(4000) 数据类型。

SQL> create or replace view v1 as select my_function col1 from dual;

View created.

SQL> desc v1;
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 COL1                                               VARCHAR2(4000)

但是，如果您将调用包装在 CAST 中，长度会发生变化

SQL> ed
Wrote file afiedt.buf

  1  create or replace view v2
  2  as
  3  select cast( my_function as varchar2(10) ) col1
  4*   from dual
SQL> /

View created.

SQL> desc v2;
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 COL1                                               VARCHAR2(10)

【讨论】：

【解决方案2】：

使用强制转换功能。在这种情况下，用 cast 包裹 get_toklen

 CAST(GET_TOKEN(GET_TOKEN(acm.PRIMARY_KEY_VALUES,1,','),2,':') as varchar2(64)) AS user_id

【讨论】：