Not only is the boolean datatype missing in Oracle’s SQL (not PL/SQL), but they also have no clear recommendation about what to use instead. See this thread on asktom. From recommending CHAR(1) 'Y"https://stackoverflow.com/"N'
they switch to NUMBER(1) 0/1
when someone points out that 'Y"https://stackoverflow.com/"N'
depends on the English language, while e.g. German programmers might use 'J"https://stackoverflow.com/"N'
instead.
The worst thing is that they defend this stupid decision just like they defend the ''=NULL
stupidity.