You have got the PATH slightly wrong. You need the PATH to “the containing directory”, not the actual executable itself.
Your PATH should be set like this:
export PATH=/Library/PostgreSQL/9.5/bin:$PATH
without the extra sql part in it. Also, you must remove the spaces around the equals sign.
Keywords: Postgresql, PATH, macOS, OSX, psql
From the Postgres documentation page:
sudo mkdir -p /etc/paths.d && echo /Applications/Postgres.app/Contents/Versions/latest/bin | sudo tee /etc/paths.d/postgresapp
restart your terminal and you will have it in your path.