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标题: oralce和db2兼容开发注意事项 [打印本页]

作者: 陈晓龙 时间: 2020-5-14 14:36
标题: oralce和db2兼容开发注意事项
这篇文章主要介绍了oralce和db2兼容开发注意事项的相关资料,这里整理了几个重要问题及如何解决，需要的朋友可以参考下

数据库兼容，在开发项目过程中，难免会遇到更改数据库，或者后期项目升级，也可能会遇到这种情况，这里就说明下oralce和db2兼容开发注意事项。
兼容oralce、db2开发注意事项（前提是db2版本是9.7，且是开启PLSQL编译选项之后创建的数据库)：

1. 在like 之后若使用了表字段，应统一改成使用locate函数

如：
oralce写法：
select * from fw_right a where '03' like a.rightid||'%';
兼容写法：
select * from fw_right a where locate('03',a.rightid) = 1;
oralce写法：
select * from fw_right a where '03' like '%'||a.rightid||'%';
兼容写法：
select * from fw_right a where locate('03',a.rightid) > 0;

2. 视图中使用的别名不应该与当前表字段同名

如以下语句，在Oracle中不会有问题，但在db2中会报"SQL0153N"错误：

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e.g:
CREATE OR REPLACE VIEW V_WF_TODOLIST AS
select c.process_def_id, c.process_def_name, a.action_def_id,
   a.work_item_id,  a.bae007,    a.action_def_name,
   a.state,    a.pre_wi_id, a.work_type,
   a.operid,    a.x_oprator_ids,  b.process_key_info,
   to_char(to_date(a.start_time,  'yyyymmddhh24miss'),'yyyy-mm-dd hh24:mi:ss') as start_time,
   to_char(to_date(a.complete_time,'yyyymmddhh24miss'),'yyyy-mm-dd hh24:mi:ss') as complete_time,
   a.filter_opr, a.memo,a.bae002,a.bae003, a.bae006,c.x_action_def_ids
from wf_work_item a, wf_process_instance b, wf_action_def c
where a.action_def_id = c.action_def_id
and b.process_def_id = c.process_def_id
and a.bae007 = b.bae007
and a.state in('0','2')

兼容写法：

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CREATE OR REPLACE VIEW V_WF_TODOLIST AS
  select c.process_def_id, c.process_def_name, a.action_def_id,
a.work_item_id,  a.bae007,    a.action_def_name,
a.state,    a.pre_wi_id, a.work_type,
a.operid,    a.x_oprator_ids,  b.process_key_info,
to_char(to_date(a.start_time,  'yyyymmddhh24miss'),'yyyy-mm-dd hh24:mi:ss') as start_time_0,
to_char(to_date(a.complete_time,'yyyymmddhh24miss'),'yyyy-mm-dd hh24:mi:ss') as complete_time_0,
a.filter_opr, a.memo,a.bae002,a.bae003, a.bae006,c.x_action_def_ids
from wf_work_item a, wf_process_instance b, wf_action_def c
where a.action_def_id = c.action_def_id
and b.process_def_id = c.process_def_id
and a.bae007 = b.bae007
and a.state in('0','2')

3.在下列情况下不允许 ORDER BY 或 FETCH FIRST n ROWS ONLY：
*  外层全查询视图
  *  "SQL 表函数"的 RETURN 语句中的外层全查询
  *  具体化查询表定义
  *  未用圆括号括起来的子查询

  否则会报"SQL20211N  规范 ORDER BY 或 FETCH FIRST n ROWS ONLY 无效。"错误.

  e.g:
oralce写法：

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CREATE OR REPLACE VIEW V_FW_BLANK_BULLETIN as
select id, bae001, operunitid, operunittype, unitsubtype, ifergency,
  title, content, digest,  duetime, validto, aae100,
  bae006, bae002, bae003,  id as colid,
  substr(digest,1,20) as digest2
from fw_bulletin
where duetime <= to_char(sysdate,'yyyymmddhh24miss')
and (to_char(validto) >= to_char(sysdate,'yyyymmddhh24miss') or validto is null)
and aae100 ='1'
order by ifergency desc, id desc, duetime desc

兼容写法：

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CREATE OR REPLACE VIEW V_FW_BLANK_BULLETIN as
select * from (select id, bae001, operunitid, operunittype, unitsubtype, ifergency,
title, content, digest, duetime, validto, aae100,
bae006, bae002, bae003, id as colid,
substr(digest,1,20) as digest2
from fw_bulletin
where duetime <= to_char(sysdate,'yyyymmddhh24miss')
and (to_char(validto) >= to_char(sysdate,'yyyymmddhh24miss') or validto is null)
and aae100 ='1'
order by ifergency desc, id desc, duetime desc)

感谢阅读，希望能帮助到大家。

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