Oracle中实现MySQL show index from table命令SQL脚本分享

实验数据初始化:

代码如下：

create table t as select * from hr.employees;

create index inx_t1 on t(employee_id,first_name desc,last_name);

create index inx_t2 on t(job_id,hire_date);

显示该表所有索引的信息。

以dba登录

代码如下：

set linesize 300;

set pagesize 100;

col c1 format a20;

col c2 format a20;

col c3 format a20;

col c4 format a20;

col c5 format a20;

col INDEX_NAME format a20;

select INDEX_NAME,

max(decode(COLUMN_POSITION,1,COLUMN_NAME||','||COLUMN_LENGTH||','||DESCEND,null)) c1,

max(decode(COLUMN_POSITION,2,COLUMN_NAME||','||COLUMN_LENGTH||','||DESCEND,null)) c2,

max(decode(COLUMN_POSITION,3,COLUMN_NAME||','||COLUMN_LENGTH||','||DESCEND,null)) c3,

max(decode(COLUMN_POSITION,4,COLUMN_NAME||','||COLUMN_LENGTH||','||DESCEND,null)) c4,

max(decode(COLUMN_POSITION,5,COLUMN_NAME||','||COLUMN_LENGTH||','||DESCEND,null)) c5

from (

select INDEX_NAME,COLUMN_NAME,COLUMN_LENGTH,COLUMN_POSITION,DESCEND

from dba_ind_columns 

where table_owner='LIHUILIN' 

AND table_name='T' 

order by INDEX_NAME,column_position

) group by INDEX_NAME;

以普通用户登录

代码如下：

set linesize 300;

set pagesize 100;

col c1 format a20;

col c2 format a20;

col c3 format a20;

col c4 format a20;

col c5 format a20;

col INDEX_NAME format a20;

select INDEX_NAME,

max(decode(COLUMN_POSITION,1,COLUMN_NAME||','||COLUMN_LENGTH||','||DESCEND,null)) c1,

max(decode(COLUMN_POSITION,2,COLUMN_NAME||','||COLUMN_LENGTH||','||DESCEND,null)) c2,

max(decode(COLUMN_POSITION,3,COLUMN_NAME||','||COLUMN_LENGTH||','||DESCEND,null)) c3,

max(decode(COLUMN_POSITION,4,COLUMN_NAME||','||COLUMN_LENGTH||','||DESCEND,null)) c4,

max(decode(COLUMN_POSITION,5,COLUMN_NAME||','||COLUMN_LENGTH||','||DESCEND,null)) c5

from (

select INDEX_NAME,COLUMN_NAME,COLUMN_LENGTH,COLUMN_POSITION,DESCEND

from user_ind_columns 

where table_name='T' 

order by INDEX_NAME,column_position

) group by INDEX_NAME;

但是可以看到,以倒序创建的索引字段，都是以SYS等命名。

Oracle把这种倒序创建的索引字段看成函数索引。

它的信息保存在user_ind_expressions视图。

user_ind_expressions视图的COLUMN_EXPRESSION字段类型是long型。

王工的版本可以解决这个问题

代码如下：

CREATE OR REPLACE FUNCTION long_2_varchar (

   p_index_name IN user_ind_expressions.index_name%TYPE,

   p_table_name IN user_ind_expressions.table_name%TYPE,

   p_COLUMN_POSITION IN user_ind_expressions.table_name%TYPE)

   RETURN VARCHAR2

AS

   l_COLUMN_EXPRESSION LONG;

BEGIN

   SELECT COLUMN_EXPRESSION

     INTO l_COLUMN_EXPRESSION

     FROM user_ind_expressions

    WHERE index_name = p_index_name

          AND table_name = p_table_name

          AND COLUMN_POSITION = p_COLUMN_POSITION;

   RETURN SUBSTR (l_COLUMN_EXPRESSION, 1, 4000);

END;

/

代码如下：

set linesize 300;

set pagesize 100;

col c1 format a20;

col c2 format a20;

col c3 format a20;

col c4 format a20;

col c5 format a20;

col INDEX_NAME format a20;

SELECT INDEX_NAME,

         MAX (DECODE (COLUMN_POSITION, 1, COLUMN_NAME || ' ' || DESCEND, NULL))

            c1,

         MAX (DECODE (COLUMN_POSITION, 2, COLUMN_NAME || ' ' || DESCEND, NULL))

            c2,

         MAX (DECODE (COLUMN_POSITION, 3, COLUMN_NAME || ' ' || DESCEND, NULL))

            c3,

         MAX (DECODE (COLUMN_POSITION, 4, COLUMN_NAME || ' ' || DESCEND, NULL))

            c4,

         MAX (DECODE (COLUMN_POSITION, 5, COLUMN_NAME || ' ' || DESCEND, NULL))

            c5

    FROM ( SELECT a.INDEX_NAME,

                   REPLACE (

                      DECODE (

                         descend,

                         'DESC', long_2_varchar (b.index_name,

                                                 b.table_NAME,

                                                 b.COLUMN_POSITION),

                         a.column_name),

                      '"',

                      '')

                      COLUMN_NAME,

                   a.COLUMN_LENGTH,

                   a.COLUMN_POSITION,

                   DESCEND

              FROM user_ind_columns a

                   LEFT JOIN

                   user_ind_expressions b

                      ON a.index_name = b.index_name

                         AND a.table_name = b.table_name

             WHERE a.table_name = 'T'

          ORDER BY INDEX_NAME, column_position)

GROUP BY INDEX_NAME;