Shell Programming and Scripting

Below is the code

Code:

nawk -F"|" 'tolower($1) ~ "abc" |"" {if (tolower($2) ~"abc"|"") print$0}' file

I want the records from file whose 1st and 2nd field should be either "abc" or "null"
I tried but its giving error.
Appreciate help

Code:

awk ' $1 ~/abc/ || $1=="" || $2 ~/abc/ || $2=="" '  inputfile

Thanks jim mcnamara
I modified the code to look for lower or uppercase.The below code was still giving output lines which did not had "abc" or null in 1st and second field.

Code:

nawk -F"|" ' tolower($1) ~ "abc" || $1=="" && tolower($2) ~"abc" || $11=="" ' file

Then i modified it as below.This does what i want.

Code:

 nawk -F"|" ' tolower($1) ~ "abc" || $1=="" {if(tolower($2) ~"abc" || $11=="") print}' file

as both the codes have the same logic
Please help me understand whats the difference.

And i see sometime we use

Code:

$1 ~/sting/

and sometime

Code:

$1 ~"string"

Please help me understand.