mysql数据库迁移greenplum讲解

1.locate(a,b)->position(a in b)

2.convert()函数不可以使用

3.ifnull(null,0.00)->COALESCE(null,0.00)

4.timestampadd(hour,24,jysj)->jysj::timestamp+'24 hour'

5.substr()->substring()

6.from_unixtime(unix_timestamp(jysj,'yyyy-MM-dd'))->to_date(jysj,'yyyy-MM-dd')

7.year(jysj)->to_char(jysj,'yyyy')

8.concat(cast(cast(nf as char),'年',jd))->nf||'年'||jd as name

9.substr(from_unix_timestamp(jysj),1,$sjd$)->substring(jysj,1,$sjd$)

10.instr(a,b)->position(a in b)

11.if(a=0,1,2)->case when a=0 then 1 else 2 end

12.if(isnull(jyye),0,jyye)->case jyye when colaesce()

13.isnull(null,0.00)->COALESCE(null,0.00)jyye then 0 else jyye end as jyye

14.date_format(jysj,'%y-%m-%d')->to_date(jysj,'yyyy-MM-dd')

15.left(jyzjhm,4)->substring(jyzjhm from 0 for 4)

16.日期函数 字符串函数

18.insertselect 对于select中的字段有顺序要求，且字段不可以少，必须对应。

19.unix_timestamp(不带引号)->to_timestamp(不带引号)

20.postgresql中没有四舍五入->可以使用cast(a as numeric)来替代round()

21.data_format(jysj,'%Y-%m')->to_date(jysj,'yyyy-MM')

22.date_add(jysj,interval 1 day) ->jysj + interval '1 day'

23.abs(round(unix_stamp(a.jysj)-unix_timestamp(b.jysj))) <$max_sjc$->

a.jysj>b.jysj and b.jysj + interval '$max_sjc$ second' < a.jysj

24.isnull(a)->a is null

25.(@rownum:=@rownum+1) -> row_number() over (order by jzje)

26.if(@pjyhm=t2,@rank:=@rank+1,@rank:=1)->row_number() over(partition by t1.jyhm order by t1.交易总金额 desc)

27.if(@pjyhm=t2.jymc,@rank:=@rank+1,@rank:=1)->row_number() over (partition by t1.jyhm order by t1.$pxfs$ desc)