当其中一个值为空（非空）时合并3列，删除多余的空格

Question

数据

col1    col2    col3 
5121     w        river road 
5512     empty    pine road 

查询1

Select LTRIM(ISNULL(Col1+' ','')+ ISNULL(col2+' ', '') + ISNULL(col3+' ','') as col4 from ...

查询2

Select LTRIM(COALESCE(Col1+' ','')+ COALESCE(col2+' ', '') + COALESCE(col3+' ','') as col4 from ...

两个结果我得到这个值

5121 w river road ( this looks good ) 
5512  pine road ( i get extra space for col 2 )

谢谢

Answer 1

问题是你有三个案例

• NULL
• 长度= 0
• 长度＆gt; 0

DEMO

CREATE TABLE Table1
    ([col1] varchar(5), [col2] varchar(5), [col3] varchar(20))
;

INSERT INTO Table1
    ([col1], [col2], [col3])
VALUES
    ('5121', 'w', 'river road'),
    ('5512', null, 'pine road'),
    ('3333', '', 'death valley')
;

SELECT COALESCE(CASE WHEN col1 = '' THEN '' ELSE col1 + ' ' END, '')  + 
       COALESCE(CASE WHEN col2 = '' THEN '' ELSE col2 + ' ' END, '')  + 
       COALESCE(CASE WHEN col3 = '' THEN '' ELSE col3 + ' ' END, '')        

FROM Table1  

<强>输出

原始OP和Jhon版本可以与NULL和length > 0一起使用，但在length = 0

时失败

Answer 2

如果2012 +

，请考虑 Concat（）

正如你可以看到col2 ... null+' '将导致null，好消息是concat（）表示空值为''

Declare @YourTable table (col1 varchar(50),col2 varchar(50),col3 varchar(50))
Insert Into @YourTable values
('5121','w', 'river road'),
('5512','','pine road'),  
('1313',null,'mocking bird lane')

Select concat(nullif(col1,'')+' ',nullif(col2,'')+' ',nullif(col3,''))
 From  @YourTable

<强>返回

5121 w river road
5512 pine road           -- No Extra Space
1313 mocking bird lane   -- NULLs handled