How to convert to date in SQL Server

Question

How can I convert single date values ​​to date? For example in C# it is possible with the following;

int year = 2019;
int day = 1;
int month = 12;
DateTime newDate = new DateTime(year, month, day); 

How is it possible in SQL Server?

I'm not asking static string value conversion such as; Convert(date, '2019-12-01') because every element (year, month, day) in date must be parameter.

Answer 1

For 2012 version or later you can use DateFromParts:

DECLARE @year VARCHAR(4) = 2019;
DECLARE @day VARCHAR(2) = 1;
DECLARE @month  VARCHAR(2) = 12;

SELECT DATEFROMPARTS ( @year, @month, @day )  

for 2008 version or higher you can use:

SELECT CAST(CAST(@year AS varchar) + '-' + CAST(@month AS varchar) + '-' + CAST(@day AS varchar) AS DATE)

Answer 2

You may try this:

 declare year varchar(5) = 2019;
 declare day varchar(2)  = 1;
 declare month varchar(2)  = 12;
 declare newDate DateTime = (select Convert(date, year + '-' + month + '-' + date));