Check if value is number

 Is this at load time (for the copy command). Or is for data that is already in the db(maybe not !)?

1) at the of data load - skip row if value is non numeric

 - i guess you need ot do it before you put data in.

 Use an ETL tool, or do it by hand in Bash 

2) data available in table - In select statement maybe in where clause

Use the projeciton_columns to identify the data type :

Ex:

select table_name,column_name,data_type from columns;

What do you want to achive by doing this ? maybe there is a better way