Thread

1. boolean over char(1)

   Thomas T. Thai <tom@minnesota.com> — 2003-01-03T19:58:46Z

   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?
   
   
   
   
   

2. Re: boolean over char(1)

   Tom Lane <tgl@sss.pgh.pa.us> — 2003-01-03T21:27:21Z

   "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
   
   

3. Re: boolean over char(1)

   Bruce Momjian <pgman@candle.pha.pa.us> — 2003-01-04T00:50:33Z

   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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4. Re: boolean over char(1)

   Tom Lane <tgl@sss.pgh.pa.us> — 2003-01-04T01:04:13Z

   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