What is the equivalent to Yes/No data type in SQL?

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What is the equivalent to Yes/No data type in SQL?

ed-1075072

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June 4, 2009 at 12:24 pm

#201169

Hi everyone!
Which SQL data type is equivalent to Yes/No [ms access]?
I am new to SQL[using sql express] and I am not sure whether BIT or Char data type is the best way to go to store booleans. I want to be able to use this column in queries.
I want to store a boolean value in this column, whethre is Yes/No, True/False or 1/0.
Thanks
Ed

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Lynn Pettis SSC Guru Points: 442467 More actions · Answer 1

Depending on how many of these values you may have in a row, I'd consider using the bit data type.

ed-1075072 Mr or Mrs. 500 Points: 596 More actions · Answer 2

Thanks Lynn,

Bit data type was what I though of using in the first place, I just wanted to make sure I can use it in queries to check whether the value of the column is true/false or yes/no.

I read a book [don't remember which one] where the author suggested to use Char(1) to store 'Y' or 'N'.

Ed

Grant Fritchey SSC Guru Points: 398909 More actions · Answer 3

You can also use a CHAR(1). A little more flexibility than bit, but then it has a little more flexibility than bit.

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GSquared SSC Guru Points: 260824 More actions · Answer 4

One problem I've run into with char(1) for this is that some clever developer somewhere along the way inevitably wants to put T/F in a column that also has Y/N, and even 1/0 (as characters). Suddenly, querying becomes really, really interesting. Check constraints can help with that.

Also takes up more space (disk and RAM) than bit. (If you have 8 bit fields per row, that's the same amount of disk/RAM as 1 char(1) field.)

In my old app that was Access on top of SQL, checkboxes worked with the bit data type, but not with Y/N or T/F char fields (of course), so another point becomes, will the front end app have to translate these, or will it deal with it more gracefully? Most app dev languages deal with 1/0 for that kind of thing more easily than with character data.

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ed-1075072 Mr or Mrs. 500 Points: 596 More actions · Answer 5

I do plan to use a check box control for this field in VB.NET

Thanks to all for the valuable information.

Ed

Grant Fritchey SSC Guru Points: 398909 More actions · Answer 6

GSquared (6/4/2009)
One problem I've run into with char(1) for this is that some clever developer somewhere along the way inevitably wants to put T/F in a column that also has Y/N, and even 1/0 (as characters). Suddenly, querying becomes really, really interesting. Check constraints can help with that.
Also takes up more space (disk and RAM) than bit. (If you have 8 bit fields per row, that's the same amount of disk/RAM as 1 char(1) field.)
In my old app that was Access on top of SQL, checkboxes worked with the bit data type, but not with Y/N or T/F char fields (of course), so another point becomes, will the front end app have to translate these, or will it deal with it more gracefully? Most app dev languages deal with 1/0 for that kind of thing more easily than with character data.

True. That's why I said that the flexibility is the weakness as well as the strength. I prefer using the bit field myself, but I've been in situations where becuase of technology or politics (usually the latter) we've been unable to.

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GSquared SSC Guru Points: 260824 More actions · Answer 7

Yeah, I got what you meant on that one, Grant. Was just expanding on it.

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PaulB-TheOneAndOnly SSC Guru Points: 66772 More actions · Answer 8

Grant Fritchey (6/4/2009)A little more flexibility than bit, but then it has a little more flexibility than bit.

not sure if this is a circular reference or quantum-logic 😀

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Grant Fritchey SSC Guru Points: 398909 More actions · Answer 9

PaulB (6/5/2009)
Grant Fritchey (6/4/2009)A little more flexibility than bit, but then it has a little more flexibility than bit.
not sure if this is a circular reference or quantum-logic 😀

Yes.

"The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood"
- Theodore Roosevelt

Author of:
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SQL Server Query Performance Tuning

Jeff Moden SSC Guru Points: 1004409 More actions · Answer 10

Depending on what is really needed outside of that column, I'll sometimes make the column a TINYINT because you can aggregate TINYINT, but not BIT. Of course, same old story of "it depends". If you want the TINYINT to have the same restrictions as a BIT for values, you'd have to put a check constraint on the column to only accept values <= 1 (or <2 or whatever).

--Jeff Moden

RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.

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Tim Walker. SSCertifiable Points: 5173 More actions · Answer 11

Nice discussion, but from the original question Yes/No, True/False, one state or the other state - has to be a bit data type doesn't it?

The business questiion is - are there ever more than two values? And after thinking hard, if there are, you probably need a tinyint (one byte) data type. Im sure from the way the question is phrased you will not need a smallint (two byte) or bigger datatype.

Tim

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Jeff Moden SSC Guru Points: 1004409 More actions · Answer 12

With that thought in mind, even the BIT datatype is tri-state... Yes, No, an dunno (NULL)

--Jeff Moden

RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.

Change is inevitable... Change for the better is not.

Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)

ed-1075072 Mr or Mrs. 500 Points: 596 More actions · Answer 13

Thank you all, It is great to hear other people's opinions, I learn a lot from others input.

Thanks again.

Ed

dmbaker SSCertifiable Points: 5139 More actions · Answer 14

PaulB (6/5/2009)
Grant Fritchey (6/4/2009)A little more flexibility than bit, but then it has a little more flexibility than bit.
not sure if this is a circular reference or quantum-logic 😀

Perhaps Mr. Fritchey works for the Department of Redundancy Department?

🙂