for i in `cat numbers.dat`
do
cat data.dat|awk -F"," '{if($1==number) print $0}' number="$i"
done > newfile.dat

">" does the redirection

What if the record's first field is "Event:number" and i want to check only for number match (neglecting Event word) against number file.

for i in `cat numbers.dat`
do
cat data.dat|awk -F"," '{if($1~/number/) print $0}' number="$i"
done > newfile.dat

~/number/ tries to match(regular expression) content of first field in the record with value in "number" variable.

its giving me error
awk: The statement cannot be correctly parsed.
The source line is 1.
syntax error The source line is 1.
The error context is
>>> {if($1*~ <<<

for number in `cat numbers.dat`
do
cat data.dat|awk -F"," '{if($1~/'$number'/) print $0}'
done

1,3,4,
1m,h,j
h2,t,y
3,f,r
4,5,h


Is this the output you were looking for ?

Yes I am looking for this kind of output however the script is not segregating records for me.