分类目录归档：Oracle 开发

1.插入一条blob数据

SQL> create directory ULTLOBDIR as '/home/oracle';

Directory created.

SQL> create table blobtest(col1 BLOB);

Table created.

SQL> declare
a_blob BLOB;
  2    3  bfile_name BFILE := BFILENAME('ULTLOBDIR','tt.txt.bak');
  4  begin
  5  insert into blobtest values (empty_blob())
  6  returning col1 into a_blob;
  7  dbms_lob.fileopen(bfile_name);
  8  dbms_lob.loadfromfile(a_blob, bfile_name, dbms_lob.getlength(bfile_name));
  9  dbms_lob.fileclose(bfile_name);
 10  commit;
 11  end;
 12  /

PL/SQL procedure successfully completed.

SQL> select dbms_lob.getlength(col1) from blobtest;

DBMS_LOB.GETLENGTH(COL1)
------------------------
                    4829

SQL> !pwd
/home/oracle

SQL> !ls -l tt.txt.bak
-rw-r--r-- 1 oracle oinstall 4829 03-19 17:26 tt.txt.bak

2.创建存储过程

CREATE OR REPLACE PROCEDURE RETRIEVE_LOB_TO_FILE(TEMP_BLOB IN BLOB,
                                                 FILE_PATH IN VARCHAR2,
                                                 FILE_NAME IN VARCHAR2) IS
  DATA_BUFFER   RAW(32767);
  POSITION      INTEGER := 1;
  FILEHANDLE    UTL_FILE.FILE_TYPE;
  ERROR_NUMBER  NUMBER;
  ERROR_MESSAGE VARCHAR2(100);
  BLOB_LENGTH   INTEGER;
  CHUNK_SIZE    BINARY_INTEGER := 32767;
BEGIN
  BLOB_LENGTH := DBMS_LOB.GETLENGTH(TEMP_BLOB);
  FILEHANDLE  := UTL_FILE.FOPEN(FILE_PATH, FILE_NAME, 'wb', 1024);
  WHILE POSITION < BLOB_LENGTH LOOP
    DBMS_LOB.READ(TEMP_BLOB, CHUNK_SIZE, POSITION, DATA_BUFFER);
    UTL_FILE.PUT_RAW(FILEHANDLE, DATA_BUFFER);
    POSITION    := POSITION + CHUNK_SIZE;
    DATA_BUFFER := NULL;
  END LOOP;
  UTL_FILE.FCLOSE(FILEHANDLE);
EXCEPTION
  WHEN OTHERS THEN
    BEGIN
      ERROR_NUMBER  := SQLCODE;
      ERROR_MESSAGE := SUBSTR(SQLERRM, 1, 100);
      DBMS_OUTPUT.PUT_LINE('Error #: ' || ERROR_NUMBER);
      DBMS_OUTPUT.PUT_LINE('Error Message: ' || ERROR_MESSAGE);
      UTL_FILE.FCLOSE_ALL;
    END;
END;
/

3.测试读取blob到系统

SQL> declare 
  2  tmp_blob blob default empty_blob(); 
  3  begin 
  4  dbms_lob.createtemporary(tmp_blob, true); 
  5  select col1 into tmp_blob from blobtest; 
  6  retrieve_lob_to_file (tmp_blob, 'ULTLOBDIR','xifenfei.txt'); 
  7  end;
  8  /

PL/SQL procedure successfully completed.

SQL> !pwd
/home/oracle

SQL> !ls -l xifenfei.txt
-rw-r--r-- 1 oracle oinstall 4829 03-20 23:44 xifenfei.txt

LNNVL官方解释
LNNVL provides a concise way to evaluate a condition when one or both operands of the condition may be null. The function can be used only in the WHERE clause of a query. It takes as an argument a condition and returns TRUE if the condition is FALSE or UNKNOWN and FALSE if the condition is TRUE. LNNVL can be used anywhere a scalar expression can appear, even in contexts where the IS [NOT] NULL, AND, or OR conditions are not valid but would otherwise be required to account for potential nulls. Oracle Database sometimes uses the LNNVL function internally in this way to rewrite NOT IN conditions as NOT EXISTS conditions. In such cases, output from EXPLAIN PLAN shows this operation in the plan table output. The condition can evaluate any scalar values but cannot be a compound condition containing AND, OR, or BETWEEN.

LNNVL官方解释翻译
lnnvl用于某个语句的where子句中的条件，如果条件为true就返回false；如果条件为UNKNOWN或者false就返回true。该函数不能用于复合条件如AND, OR, or BETWEEN中。

模拟测试环境

SQL> create table xifenfei(name varchar2(20),year number);

Table created.

SQL> insert into xifenfei values('xifenfei2001',2001);

1 row created.

SQL> insert into xifenfei values('xifenfei2002',2002);

1 row created.

SQL> insert into xifenfei values('xifenfei2003',2003);

1 row created.

SQL> insert into xifenfei values('xifenfei2004',2004);

1 row created.

SQL> insert into xifenfei values('xifenfei2005',2005);

1 row created.

SQL> insert into xifenfei values('xifenfei2006',2006);

1 row created.

SQL> insert into xifenfei values('xifenfei2007',2007);

1 row created.

SQL> insert into xifenfei values('xifenfei2008',null);

1 row created.

SQL> insert into xifenfei values('xifenfei2009',2009);

1 row created.

SQL> insert into xifenfei values('xifenfei2010',2010);

1 row created.

SQL> insert into xifenfei values('xifenfei2011',2011);

1 row created.

SQL> commit;

Commit complete.

SQL> select * from xifenfei;

NAME                       YEAR
-------------------- ----------
xifenfei2001               2001
xifenfei2002               2002
xifenfei2003               2003
xifenfei2004               2004
xifenfei2005               2005
xifenfei2006               2006
xifenfei2007               2007
xifenfei2008
xifenfei2009               2009
xifenfei2010               2010
xifenfei2011               2011

11 rows selected.

几种情况测试说明

--年份小于2009(lnnvl表示年份大于或者2009包含null)
SQL> select * from xifenfei where lnnvl(year<2009);

NAME                       YEAR
-------------------- ----------
xifenfei2008
xifenfei2009               2009
xifenfei2010               2010
xifenfei2011               2011

--year不为null(lnnvl表示年份为null)
SQL> select * from xifenfei where lnnvl(year is not null);

NAME                       YEAR
-------------------- ----------
xifenfei2008

--年份为null(lnnvl表示年份不为null)
SQL> select * from xifenfei where lnnvl(year is  null);

NAME                       YEAR
-------------------- ----------
xifenfei2001               2001
xifenfei2002               2002
xifenfei2003               2003
xifenfei2004               2004
xifenfei2005               2005
xifenfei2006               2006
xifenfei2007               2007
xifenfei2009               2009
xifenfei2010               2010
xifenfei2011               2011

10 rows selected.

--年份为12345(lnnvl表示年份不为12345)
SQL> select * from xifenfei where lnnvl(year =12345);

NAME                       YEAR
-------------------- ----------
xifenfei2001               2001
xifenfei2002               2002
xifenfei2003               2003
xifenfei2004               2004
xifenfei2005               2005
xifenfei2006               2006
xifenfei2007               2007
xifenfei2008
xifenfei2009               2009
xifenfei2010               2010
xifenfei2011               2011

11 rows selected.

--年份不为12345(lnnvl表示年份为12345或者null)
SQL> select * from xifenfei where lnnvl(year !=12345);

NAME                       YEAR
-------------------- ----------
xifenfei2008