where - SQL Combine same bind variable -

i have clause says:

select * tablename  :x < y or y null  , :x > z 

i tried rewrite uses :x once shown below don't understand why keep getting error says 'sql command not ended'.

where z < :x < y or y null 

any appreciated, thanks.

the expression trying use z < x < y not standard sql.

you can come close with:

where :x between y , z or y null; 

the difference between 'y <= x <= z'. if inequality needed , values integers, can do:

where :x between y + 1 , z - 1 or y null;