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

时间:2014-10-31 11:30来源:网络整理 作者:网络 点击:
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这篇文章主要介绍了Oracle中实现MySQL show index from table命令SQL脚本分享,本文只是模拟了Mysql中的show index from table命令,需要的朋友可以参考下

实验数据初始化:

复制代码 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

复制代码 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

复制代码 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

复制代码 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;
/


复制代码 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;


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