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Thread: boolean over char(1)

boolean over char(1)

From
"Thomas T. Thai"
Date:
Is there any advantages of using datatype boolean over char(1)? If there
isn't I think char(1) is more portable across other DBM?

Re: boolean over char(1)

From
Tom Lane
Date:
"Thomas T. Thai" <tom@minnesota.com> writes:
> Is there any advantages of using datatype boolean over char(1)?

boolean fits in 1 byte; char(1) requires 5 bytes (maybe more, depending
on alignment considerations).

boolean will be considerably faster to operate on, being pass-by-value.

char(1) will happily accept values that don't correspond to booleans
(eg, if you use 't' and 'f' to represent booleans in a char(1), what
will you do with 'y' or 'z'?)  You could possibly fix that with a
check constraint, but that slows things down still more.

boolean is, um, boolean: it behaves as expected in boolean expressions.
You can't do AND, OR, NOT directly on chars.


> If there isn't I think char(1) is more portable across other DBM?

The boolean datatype is standard in SQL99.

            regards, tom lane

Re: boolean over char(1)

From
Bruce Momjian
Date:
Also, we do support "char", which is one byte.  You need to specify the
quotes when creating the column.

---------------------------------------------------------------------------

Tom Lane wrote:
> "Thomas T. Thai" <tom@minnesota.com> writes:
> > Is there any advantages of using datatype boolean over char(1)?
>
> boolean fits in 1 byte; char(1) requires 5 bytes (maybe more, depending
> on alignment considerations).
>
> boolean will be considerably faster to operate on, being pass-by-value.
>
> char(1) will happily accept values that don't correspond to booleans
> (eg, if you use 't' and 'f' to represent booleans in a char(1), what
> will you do with 'y' or 'z'?)  You could possibly fix that with a
> check constraint, but that slows things down still more.
>
> boolean is, um, boolean: it behaves as expected in boolean expressions.
> You can't do AND, OR, NOT directly on chars.
>
>
> > If there isn't I think char(1) is more portable across other DBM?
>
> The boolean datatype is standard in SQL99.
>
>             regards, tom lane
>
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Re: boolean over char(1)

From
Tom Lane
Date:
Bruce Momjian <pgman@candle.pha.pa.us> writes:
> Also, we do support "char", which is one byte.  You need to specify the
> quotes when creating the column.

But he's looking for "more standard", which "char" surely is not.

            regards, tom lane