[大数据]hive字段关联类型不一致时，两边都会转换成double类型

--hive字段关联类型不一致时，两边都会转换成double类型

explain

select a.*,b.*

from (

select cast(186994576061124660 as bigint) col ) a

left join (select '186994576061124672' as col ) b on a.col=b.col ;

186994576061124660 186994576061124672

Reduce Operator Tree:

Join Operator

condition map:

Left Outer Join0 to 1

keys:

0 UDFToDouble(186994576061124660) (type: double)

1 UDFToDouble('186994576061124672') (type: double)

--不一致时人工转成string

explain

select a.*,b.*

from (

select cast(186994576061124660 as bigint) col ) a

left join (select '186994576061124672' as col ) b on cast(a.col as string)=b.col;

186994576061124660 NULL

Reduce Operator Tree:

Join Operator

condition map:

Left Outer Join0 to 1

keys:

0 UDFToString(186994576061124660) (type: string)

1 '186994576061124672' (type: string)

select '186994576061124660' , cast(186994576061124660 as double) as dl,cast(186994576061124660 as bigint) as bt,cast(186994576061124660 as decimal) as dm

union all

select '186994576061124559' , cast(186994576061124559 as double) as dl,cast(186994576061124559 as bigint) as bt,cast(186994576061124559 as decimal) as dm

186994576061124660 1.86994576061124672E17 186994576061124660 NULL

186994576061124559 1.86994576061124544E17 186994576061124559 NULL

select if(cast(186994576061124660 as double)='186994576061124660',1,0)

1

select if(cast(186994576061124660 as double)='186994576061124672',1,0)

1

select if(cast(186994576061124660 as bigint)='186994576061124672',1,0);

WARNING: Comparing a bigint and a string may result in a loss of precision.

1