Is there any boolean type in Oracle databases?

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'/'N' they switch to NUMBER(1) 0/1 when someone points out that 'Y'/'N' depends on the English language, while e.g. German programmers might use 'J'/'N' instead.

The worst thing is that they defend this stupid decision just like they defend the ''=NULL stupidity.

Nope.

Can use:

IS_COOL NUMBER(1,0)

1 - true
0 - false

--- enjoy Oracle

Or use char Y/N as described here

As per Ammoq and kupa's answers, We use number(1) with default of 0 and don't allow nulls.

here's an add column to demonstrate:

ALTER TABLE YourSchema.YourTable ADD (ColumnName NUMBER(1) DEFAULT 0 NOT NULL);

Hope this helps someone.

No, there isn't a boolean type in Oracle Database, but you can do this way:

You can put a check constraint on a column.

If your table hasn't a check column, you can add it:

ALTER TABLE table_name
ADD column_name_check char(1) DEFAULT '1';

When you add a register, by default this column get 1.

Here you put a check that limit the column value, just only put 1 or 0

ALTER TABLE table_name ADD
CONSTRAINT name_constraint 
column_name_check (ONOFF in ( '1', '0' ));