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我們?cè)谧黾嫒?strong>oralce、db2開(kāi)發(fā)時(shí)，需要注意一些問(wèn)題，以免遇到不兼容的現(xiàn)象，為開(kāi)發(fā)者帶來(lái)麻煩。本例子的前提是db2版本是9.7，且是開(kāi)啟PLSQL編譯選項(xiàng)之后創(chuàng)建的數(shù)據(jù)庫(kù)。接下來(lái)我們就開(kāi)始介紹這些。
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注意事項(xiàng)：
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(xiě)法：
- select * from fw_right a where '03' like a.rightid||'%';
兼容寫(xiě)法：
- select * from fw_right a where locate('03',a.rightid) = 1;
oralce寫(xiě)法：
- select * from fw_right a where '03' like '%'||a.rightid||'%';
兼容寫(xiě)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(yǔ)句，在oracle中不會(huì)有問(wèn)題，但在db2中會(huì)報(bào)"SQL0153N"錯(cuò)誤。
- 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(xiě)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(yǔ)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(lái)的子查詢
否則會(huì)報(bào)"SQL20211N 規(guī)范 ORDER BY 或 FETCH FIRST n ROWS ONLY 無(wú)效。"錯(cuò)誤。
oralce寫(xiě)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(xiě)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)
了解了以上Oracle、DB2開(kāi)發(fā)時(shí)的注意事項(xiàng)，我們?cè)谧鲩_(kāi)發(fā)的時(shí)候就能夠盡量避免一些不兼容得狀況了。本文就介紹到這里，希望能對(duì)各位有所幫助。
網(wǎng)站欄目：談一談兼容Oracle和DB2開(kāi)發(fā)時(shí)的注意事項(xiàng)
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