how to expand variable within single quotes and would give output within single quotes using bash

I would like to expand one variable in bash and would like to get result within single quotes itself.

for example , my script below includes:

    sqlplus -s user/password
    select sys_context
    Where schemaname = '$USERNAME'

I would like to expand it as:

   Where schemaname = 'XYZ_OWNER'

I tried something like :

   where schemaname = "'""$USERNAME""'"

But it is throwing me below error:

   where schemaname = "'"XYZ_OWNER""'"

Please suggest how can this be resolved.

>Solution :

To get parameter expansion without wordsplitting, double quotes are used. Example:

USERNAME=fluffy
where_clause="where schemaname = '$USERNAME'"

This sets the variable where_clause to the value where schemaname = 'fluffy'.