這兩天要把一個系統(tǒng)從oracle上移植到mysql上，順便簡單整理一下兩者語法的不同

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decode

mysql中沒有decode,可以使用case when語句代替，oracle也支持case when語句，看來以后為了移植方便還是使用case when比較好。

select NAME,case namewhen 'sam' then 'yong'when 'lee' then 'handsome'else 'good' end from lee;

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下面是同一條sql,decode與case when比較：

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sum(decode(sign(similarity-${param1})+sign(similarity-${param2}),0,1,-1,1,0)) as sus_tort_countsum(case sign(similarity-${param1})+sign(similarity-${param2}) when 0 then 1 when -1 then 1 else 0 End

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2.分頁代碼：

oracle中分頁代碼使用rownum,具體參見：http://qingfeng825.iteye.com/blog/779462

----oracle排序?qū)懛? SELECT * FROM ( SELECT list.*, rownum as RNUM FROM ( SELECT * FROM CIP_Test_User ORDER BY ID desc ) list WHERE ROWNUM < 11 ) WHERE RNUM >=1

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1和11都代表行號

mysql分頁使用limit

----mysql排序?qū)懛? SELECT * FROM CIP_Test_User ORDER BY ID desc limit 1,10

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1代表偏移量，10代表要取出來的記錄個數(shù)

3.數(shù)字轉(zhuǎn)字符串

???? mysql:? concat(site_id,'')

???? oracle:to_char(site_id)

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4.取當(dāng)前日期(mysql 要加括號)

??? mysql:now()，sysdate() 具體參見:http://blog.sina.com.cn/s/blog_6d39dc6f0100m7eo.html

??? oracle:sysdate

5.觸發(fā)器的不同，下面是兩個相同功能的觸發(fā)器

CREATE TRIGGER `IMS_EVIDENCE_UPDATE_TRIGGER` BEFORE UPDATE ON `bas_page_evidence`FOR EACH ROW BEGIN if ((NEW.WEB_IMAGE IS NOT NULL AND OLD.WEB_IMAGE IS NULL) OR(NEW.WEB_URL_IMAGE IS NOT NULL AND OLD.WEB_URL_IMAGE IS NULL) OR(NEW.HTML_SNAP IS NOT NULL AND OLD.HTML_SNAP IS NULL)) thenset new.Evidence_Done_Count=new.Evidence_Done_Count+1;if(new.EVIDENCE_DONE_COUNT>=new.EVIDENCE_COUNT) thenset new.Evidence_date=sysdate();if(new.EVIDENCE_STATUS!='4' and old.EVIDENCE_STATUS!='4') thenset new.Evidence_status = '3';end if;update bas_monitor_result set status='5' where status='4' and url_Id=new.url_id;end if; end if; END;

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CREATE OR REPLACE TRIGGER IMS_EVIDENCE_UPDATE_TRIGGER before UPDATE OF Web_image,Web_url_image,Html_snap ON ims_page_evidence REFERENCING NEW AS NEW OLD AS OLD FOR EACH ROW WHEN ((new.Web_image is not null and old.Web_image is null) or(new.Web_url_image is not null and old.Web_url_image is null) or(new.Html_snap is not null and old.Html_snap is null)) BEGIN:new.Evidence_Done_Count := :old.Evidence_Done_Count+1;if :old.Evidence_Done_Count+1 >= :old.Evidence_Count then:new.Evidence_date := sysdate;if :old.Evidence_status !='4' and :new.Evidence_status !='4' then:new.Evidence_status := '3';end if;--更新resultupdate ims_monitor_result set status='5' where status='4' and url_Id=:new.url_id;end if; END;

(oracle版本)?

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?幾點不同： mysql沒有replace trigger, 要修改一個trigger只能是drop trigger后重新建；

???????????????? oracle在before update? 與 on? 表名之間可以加入 of 列名1，列名2，列表3，表示當(dāng)前trigger只對這幾列有用，在mysql中沒有找到這種寫法。

???????????????? oracle中用到new old都要加: ，mysql不用。

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