Teradata recommends a data skew threshold of no more than 5% across the AMPs . It is a rule of thumb, but not absolute. Small tables can be skew by their nature.
select
hashamp(hashbucket(hashrow(<PRIMARY_INDEX>))) as "AMP",
count(*) as "row count",
"row count" * 100.00 / sum("row count") over() as "% of total rows",
cast((max("row count") over() - min("row count") over()) * 100.00 /
nullif(min("row count") over(),0)
as decimal(9,2)) as "Teradata variance %",
case
when "Teradata variance %" < 5
then 'pass'
else 'fail'
end as "Teradata threshold (5%)"
from <DATABASE_NAME>.<TABLE_NAME>
group by 1
order by 1;
Example:
select
hashamp(hashbucket(hashrow(Sales_Tran_Seq_Num))) as "AMP",
count(*) as "row count",
"row count" * 100.00 / sum("row count") over() as "% of total rows",
cast((max("row count") over() - min("row count") over()) * 100.00 /
nullif(min("row count") over(),0)
as decimal(9,2)) as "Teradata variance %",
case
when "Teradata variance %" < 5
then 'pass'
else 'fail'
end as "Teradata threshold (5%)"
from DB.SALES_TRANSACTION
group by 1
order by 1;