Tinyint vs Bit?

Question

I don\'t want to touch-off a religious war here, but there seem to be two schools of thoughts in how to represent boolean values in a database. Some say bit is

Answer 1

@Kevin: I believe you can use group by on bit fields (SQL Server 2005):

declare @t table (
    descr varchar(10),
    myBit1 bit, 
    myBit2 bit
)
insert into @t values ('test1', 0, 1)
insert into @t values ('test2', 1, 0)
insert into @t values ('test3', 1, 1)
insert into @t values ('test4', 0, 0)

select myBit1, count(myBit1) from @t group by myBit1
select myBit2, count(myBit1) from @t group by myBit2

Results:

myBit1 
------ -----------
0      2
1      2

myBit2 
------ -----------
0      2
1      2

Answer 2

TinyInt is my preference. Then, when doing aggregated counts against the field, you don't have to cast it. Also, some front-end languages interpret a Bit differently than others, and using a TinyInt makes validation checks universal for any front-end language.

Answer 3

Bit...unless you're of the "true / false / file not found" clan

In case you didn't get the reference...

And in the case of Linq2SQL, bit works with true/false which makes it easier to program for. There's advantages to both.

And there's also programming maintenance to consider. What happens if you (or a junior intern programmer) uses a 2, 3, 25, 41, 167, 200 etc? Where is that documented? Bits are self-documenting and pretty universal.

Answer 4

For MySql users - Why you should not use BIT columns in MySQL

Answer 5

I use bit because it saves me having to use a check constraint, and because my ORM will automatically convert bit into a nullable boolean (C#), which I very much appreciate once coding.

Answer 6

I use bits when appropriate. Aside from it being semantically the correct type (semantics count!), multiple bit fields (up to 8) in a single row (on SQL Server, anyway) can be consolidated into a single byte of storage. After the eighth, an additional byte is needed for the next 8, and so on.

References:

• SQL 2000
• SQL 2005
• SQL 2008