--sqlserver 2012之前的版本

/* 处理not null字符 */

DECLARE @t1 varchar(10) = 'a'

DECLARE @t2 varchar(10) = 'b'

DECLARE @t3 varchar(10) = 'c'

DECLARE @t4 varchar(10) = 'd'

DECLARE @N1 int = 2012

SELECT @t1+@t2+@t3+@t4+convert(varchar(10),@N1 ) as result

go

/* 处理 null字符 */

DECLARE @t1 varchar(10) = 'a'

DECLARE @t2 varchar(10) = 'b'

DECLARE @t3 varchar(10) = null

DECLARE @t4 varchar(10) = 'd'

DECLARE @N1 int = 2012

SELECT @t1+@t2+ISNULL(@t3,'')+@t4+convert(varchar(10),@N1 ) as result

GO

如果这里不使用isnull判断，那么我们获得的值将为null, 与我们期望的大相径庭.

---sqlserver 2012中

 

SELECT CONCAT('a','b','c','d','2012') as result

go

/* 处理not null字符 */

DECLARE @t1 varchar(10) = 'a'

DECLARE @t2 varchar(10) = 'b'

DECLARE @t3 varchar(10) = 'c'

DECLARE @t4 varchar(10) = 'd'

DECLARE @N1 int = 2012

SELECT CONCAT(@t1, @t2, @t3, @t4, @N1) as result

go

/* 处理 null字符 */

DECLARE @t1 varchar(10) = 'a'

DECLARE @t2 varchar(10) = 'b'

DECLARE @t3 varchar(10) = null

DECLARE @t4 varchar(10) = 'd'

DECLARE @N1 int = 2012

SELECT CONCAT(@t1, @t2, @t3, @t4, @N1) as result

go