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

浅沫记忆

实验数据初始化:

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

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

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

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;
/

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;