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Oracle中實(shí)現(xiàn)MySQL show index from table命令SQL腳本分享

更新時(shí)間：2014年10月30日 11:01:06 投稿：junjie

這篇文章主要介紹了Oracle中實(shí)現(xiàn)MySQL show index from table命令SQL腳本分享,本文只是模擬了Mysql中的show index from table命令,需要的朋友可以參考下

實(shí)驗(yàn)數(shù)據(jù)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);

顯示該表所有索引的信息。

以dba登錄

復(fù)制代碼代碼如下:

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;

以普通用戶登錄

復(fù)制代碼代碼如下:

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,以倒序創(chuàng)建的索引字段，都是以SYS等命名。

Oracle把這種倒序創(chuàng)建的索引字段看成函數(shù)索引。

它的信息保存在user_ind_expressions視圖。

user_ind_expressions視圖的COLUMN_EXPRESSION字段類型是long型。

王工的版本可以解決這個(gè)問(wèn)題

復(fù)制代碼代碼如下:

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;
/

復(fù)制代碼代碼如下:

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;

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