Data Modeling | Interview Questions & Answers

[saritapatel]

It covered almost all basic concepts of Data modeling

[suryamurthyvanamoju]

can you please check the answer to the last question
When a unique constraint gets applied to a column, does it generate an error if you attempt to place two NULLs in it?

I'm sure the answer is Yes, it'll raise an error as "Cannot insert duplicate key in object 'dbo.T1'. The duplicate key value is (<NULL>)."


DROP TABLE IF EXISTS T1
CREATE TABLE T1 (
ID int NULL UNIQUE
);

insert into t1(Id) values (1);
select row_number() OVER(Order by (SELECT 1)) AS Sno, * from t1;

insert into t1(Id) values (null);
select row_number() OVER(Order by (SELECT 1)) AS Sno, * from t1;

insert into t1(Id) values (null);
select row_number() OVER(Order by (SELECT 1)) AS Sno, * from t1;

[MilhouseBS]

“Conformed” dimensions, not “confirmed”.