Question

Regarding to SQL performance.

I have a scalar valued function for checking some specific condition in base, it returns BIT value for True or False.

I now do not know how I should fill @BIT parameter

If I write.

set @bit = convert(bit,1)

or

set @bit = 1

or

set @bit='true'

function will work anyway but I do not know which method is recommended for daily use.

Another question, I have table in my base with around 4 million records, daily insert is about 4K records in that table.

Now I want to add CONSTRAINT on that table with scalar valued function that I mentioned already

Something like this

ALTER TABLE fin_stavke
ADD CONSTRAINT fin_stavke_knjizenje CHECK ( dbo.fn_ado_chk_fin(id)=convert(bit,1))

where “id” is the primary key of table fin_stavke and dbo.fn_ado_chk_fin looks like

create FUNCTION fn_ado_chk_fin
(
    @stavka_id int
)
RETURNS bit
AS
BEGIN
declare @bit bit

if exists (select * from fin_stavke where id=@stavka_id and doc_id is null and protocol_id is null)
        begin
            set @bit=0


        end
    else
        begin
            set @bit=1
        end
return @bit;
END
GO

Will this type and method of checking constraint will affect badly performance on my table and SQL at all ?

If there is also better way to add control on this table please let me know.

Answer 1

I might be wrong but from the looks of it, it seems you only want to check that not both doc_id and protocol_id are NULL?

You can add a table constraint to achieve this.

ALTER TABLE fin_stavke
ADD CONSTRAINT fin_stavke_knjizenje CHECK ( doc_id IS NOT NULL OR protocol_id IS NOT NULL)