Oracle数据字典中long字段的查询

Oracle数据字典中long字段的查询

-- Oracle数据字典中long字段的查询

-- 在数据字典中保留很多long字段，查询时很不方便。
-- 以下包可以转换为varchar2方便操作，查询数据字典时可以用varchar进行查询

CREATE OR REPLACE PACKAGE long_help AUTHID CURRENT_USER AS
  FUNCTION substr_of(p_query IN VARCHAR2,
                     p_from  IN NUMBER,
                     p_for   IN NUMBER,
                     p_name1 IN VARCHAR2 DEFAULT NULL,
                     p_bind1 IN VARCHAR2 DEFAULT NULL,
                     p_name2 IN VARCHAR2 DEFAULT NULL,
                     p_bind2 IN VARCHAR2 DEFAULT NULL,
                     p_name3 IN VARCHAR2 DEFAULT NULL,
                     p_bind3 IN VARCHAR2 DEFAULT NULL,
                     p_name4 IN VARCHAR2 DEFAULT NULL,
                     p_bind4 IN VARCHAR2 DEFAULT NULL) RETURN VARCHAR2;
END;
/
CREATE OR REPLACE PACKAGE BODY long_help AS

  g_cursor NUMBER := dbms_sql.open_cursor;
  g_query  VARCHAR2(32765);

  PROCEDURE bind_variable(p_name IN VARCHAR2, p_value IN VARCHAR2) IS
  BEGIN
    IF (p_name IS NOT NULL) THEN
      dbms_sql.bind_variable(g_cursor
                            ,p_name
                            ,p_value);
    END IF;
  END;
  --使用方法：
  /*SELECT LONG_HELP.SUBSTR_OF(''||
       'SELECT data_default '||
       '  FROM user_tab_columns '||
       ' WHERE table_name  = '''||t.table_name ||''''||
       '   AND column_name = '''||t.column_name||''''||
       '',1,4000) AS data_default
  FROM user_tab_columns t;*/
  FUNCTION substr_of(p_query IN VARCHAR2,
                     p_from  IN NUMBER,
                     p_for   IN NUMBER,
                     p_name1 IN VARCHAR2 DEFAULT NULL,
                     p_bind1 IN VARCHAR2 DEFAULT NULL,
                     p_name2 IN VARCHAR2 DEFAULT NULL,
                     p_bind2 IN VARCHAR2 DEFAULT NULL,
                     p_name3 IN VARCHAR2 DEFAULT NULL,
                     p_bind3 IN VARCHAR2 DEFAULT NULL,
                     p_name4 IN VARCHAR2 DEFAULT NULL,
                     p_bind4 IN VARCHAR2 DEFAULT NULL) RETURN VARCHAR2 AS
    l_buffer     VARCHAR2(4000);
    l_buffer_len NUMBER;
  BEGIN
    IF (nvl(p_from
           ,0) <= 0) THEN
      raise_application_error(-20002
                             ,'From must be >= 1 (positive numbers)');
    END IF;
    IF (nvl(p_for
           ,0) NOT BETWEEN 1 AND 4000) THEN
      raise_application_error(-20003
                             ,'For must be between 1 and 4000');
    END IF;
  
    IF (p_query <> g_query OR g_query IS NULL) THEN
      IF (upper(TRIM(nvl(p_query
                        ,'x'))) NOT LIKE 'SELECT%') THEN
        raise_application_error(-20001
                               ,'This must be a select only');
      END IF;
      dbms_sql.parse(g_cursor
                    ,p_query
                    ,dbms_sql.native);
      g_query := p_query;
    END IF;
    bind_variable(p_name1
                 ,p_bind1);
    bind_variable(p_name2
                 ,p_bind2);
    bind_variable(p_name3
                 ,p_bind3);
    bind_variable(p_name4
                 ,p_bind4);
  
    dbms_sql.define_column_long(g_cursor
                               ,1);
    IF (dbms_sql.execute_and_fetch(g_cursor) > 0) THEN
      dbms_sql.column_value_long(g_cursor
                                ,1
                                ,p_for
                                ,p_from - 1
                                ,l_buffer
                                ,l_buffer_len);
    END IF;
    RETURN l_buffer;
  END substr_of;

END;
/

-- 使用(调用)方法：
SELECT LONG_HELP.SUBSTR_OF(''||
       'SELECT data_default '||
       '  FROM user_tab_columns '||
       ' WHERE table_name  = '''||t.table_name ||''''||
       '   AND column_name = '''||t.column_name||''''||
       '',1,4000) AS data_default
      ,t.*
  FROM user_tab_columns t;