Sql语句中如何判断空字符串？

[spring0906]

Sql语句中如何判断空字符串？

我的存储过程是这样：
CREATE PROCEDURE employees_select_SQL_proc
@name nvarchar(20),
@did nvarchar(3),
@work nvarchar(10),
@rid nvarchar(3)
AS
DECLARE @sql nvarchar(1000)
SET @sql='SELECT * FROM employees WHERE 1=1'
IF(@name IS NOT NULL)
BEGIN
SET @sql=@sql+' AND E_name LIKE ''%'+@name+'%'' '
END
IF(@did IS NOT NULL)
BEGIN
SET @sql=@sql+' AND E_Did ='+@did
END
IF(@work IS NOT NULL)
BEGIN
SET @sql=@sql+' AND E_work LIKE ''%'+@work+'%'' '
END
IF(@rid IS NOT NULL)
BEGIN
SET @sql=@sql+' AND E_Rid ='+@rid
END
EXEC(@sql)
GO

当我在页面调用这个存储过程的时候，每个参数有3中情况：
1，null
2,“”（空字符串）
3，有值

我只判断了第一种，在存储过程中怎么判断这3中情况啊？

[dawugui]

没看懂.帮顶.

[SmileShark]

if @name=' '
begin
end
就可以了吧

[百年树人]

[Quote=引用楼主 spring0906 的帖子:]
Sql语句中如何判断空字符串？

我的存储过程是这样：
CREATE PROCEDURE employees_select_SQL_proc
@name nvarchar(20),
@did nvarchar(3),
@work nvarchar(10),
@rid nvarchar(3)
AS
DECLARE @sql nvarchar(1000)
SET @sql='SELECT * FROM employees WHERE 1=1'
IF(@name IS NOT NULL)
BEGIN
SET @sql=@sql+' AND E_name LIKE ''%'+@name+'%'' '
END
IF(@did IS NOT NULL)
BEGIN
SET @sql=@sq…
[/Quote]

--1，null 
where col is null
--2,“”（空字符串） 
where len(col)=0
--3，有值 
where col is not null

?

[百年树人]

--3，有值 
where len(col)>0 

[ks_reny]

 where A is null   當A為null時
  where A=''       當A為空時
  where A='某個值'  當A有值時

[ai_li7758521]

if @name is null
begin
    ...
end
else if @name=''
begin
    ...
end
else
begin
    ....
end  

[zejyu]

...
IF isnull(@name,'')<>'' SET @sql=@sql+' AND E_name LIKE ''%'+@name+'%'' '
IF isnull(@did,'')<>'' SET @sql=@sql+' AND E_Did ='+@did
IF isnull(@work,'')<>'' SET @sql=@sql+' AND E_work LIKE ''%'+@work+'%'' '
IF isnull(@rid,'')<>'' SET @sql=@sql+' AND E_Rid ='+@rid
...