sql server 时间拼接

DECLARE @casetime NVARCHAR(30);
DECLARE @year NVARCHAR(30);
SET @year ='2015'


IF  CAST(@year AS INT) = YEAR(GETDATE())
BEGIN 
SET @casetime = CAST(@year AS NVARCHAR(30))+'-'+ (CASE WHEN Len(MONTH(GETDATE()))=1 THEN '0'+ CAST( MONTH(GETDATE()) AS NVARCHAR(30) ) ELSE   CAST( MONTH(GETDATE()) AS NVARCHAR(30)) END)+'-01'
END
ELSE
BEGIN 
SET @casetime = @year+'-01-01'
END
SELECT @casetime