數(shù)據(jù)庫兼容，在開發(fā)項(xiàng)目過程中，難免會(huì)遇到 更改數(shù)據(jù)庫，或者后期 項(xiàng)目升級(jí)，也可能會(huì)遇到這種情況，這里就說明下oralce和db2兼容開發(fā)注意事項(xiàng)。
兼容oralce、db2開發(fā)注意事項(xiàng)（前提是db2版本是9.7，且是開啟PLSQL編譯選項(xiàng)之后創(chuàng)建的數(shù)據(jù)庫)：
1. 在like 之后若使用了表字段，應(yīng)統(tǒng)一改成使用locate函數(shù)
如：
oralce寫法：
select * from fw_right a where '03' like a.rightid||'%';
兼容寫法：
select * from fw_right a where locate('03',a.rightid) = 1;
oralce寫法：
select * from fw_right a where '03' like '%'||a.rightid||'%';
兼容寫法：
select * from fw_right a where locate('03',a.rightid) > 0;
2. 視圖中使用的別名不應(yīng)該與當(dāng)前表字段同名
如以下語句，在Oracle中不會(huì)有問題，但在db2中會(huì)報(bào)"SQL0153N"錯(cuò)誤：
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')
兼容寫法：
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.在下列情況下不允許 ORDER BY 或 FETCH FIRST n ROWS ONLY：
* 外層全查詢視圖
* "SQL 表函數(shù)"的 RETURN 語句中的外層全查詢
* 具體化查詢表定義
* 未用圓括號(hào)括起來的子查詢
否則會(huì)報(bào)"SQL20211N 規(guī)范 ORDER BY 或 FETCH FIRST n ROWS ONLY 無效。"錯(cuò)誤.
e.g:
oralce寫法：
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
兼容寫法：
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)
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