oracle - 在 Oracle 中创建 View 时更改列精度

Question

 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 View 时，get_token() 函数使列类型成为 varchar2(4000)。如何更改命令，使其成为 varchar2(64) 字段？

Answer 1

您可以使用 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.

那么一个选择这个函数的简单 View 会有一个 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)

如果您将调用包裹在 CAST 中，然而，长度改变

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)