當我在撇號之前刪除一些空格時，爲什麼字符串連接失敗？

Question

這工作：

DECLARE @query as nvarchar(200); 
SET @query = 'SELECT j.job FROM ' + '' + 'job as j'; 

EXEC sp_executesql @query 

...但是這不工作（輸出誤差是Incorrect syntax near the keyword 'as', pointing to the first line）：

DECLARE @query as nvarchar(200); 
SET @query = 'SELECT j.job FROM' + '' + 'job as j'; -- removed the white space after the word FROM 

EXEC sp_executesql @query 

這是爲什麼？

Answer 1

因爲之前需要from之後的空格。

select 'SELECT j.job FROM ' + '' + 'job as j'; 

回報：SELECT j.job FROM job as j

select 'SELECT j.job FROM' + '' + 'job as j'; 

回報：SELECT j.job FROMjob as j