When designing databases, what is the preferred way to store multiple true / false values?

Question

As stated in the title, when designing databases, what is the preferred way to handle tables that have multiple columns that are just storing true / false values as just a single either or value (e.g. "Y/N: or "0/1")? Likewise, are there some issues that might arise between different databases (e.g. Oracle and SQL Server) that might affect how the columns are handled?

Answer 1

In SQL Server, there is BIT datatype. You can store 0 or 1 there, compare the values but not run MIN or MAX.

In Oracle, you just use NUMBER or CHAR(1).

In MySQL and PostgreSQL any datatype is implicitly convertible to BOOLEAN.

Both systems support BOOLEAN datatype which you can use as is, without the operators, in the WHERE or ON clauses:

SELECT  *
FROM    mytable
WHERE   col1

, which is impossible in SQL Server and Oracle (you need to have some kind or a predicate there).

In MySQL, BOOLEAN is a synonym for TINYINT(1).

In PostgreSQL too (in terms of storage), but logically, it's not implicitly convertible to any other type.