沒有動態SQL的動態搜索

Question

用戶可以按名字，姓氏搜索客戶，也可以選擇輸入城市。

只有當用戶使用動態SQL輸入一個W/O時，纔可以編寫與CITY相匹配的SQL？

CREATE PROCEDURE [dbo].[SearchCustomer] 
@FirstName varchar(30) --REQUIRED 
@LastName varchar(30)--REQUIRED 
@City varchar(30) --OPTIONAL 
AS 
SELECT * FROM CUSTOMER C WHERE 
C.FirstName = @FirstName AND 
C.LastName = @LastName AND 
C.City = IsNull(@City, C.City) --This won't Work if CITY is optional in the database 

Answer 1

嘗試：

(@City is null OR C.City = @City) 

Answer 2

試試這個

COALESCE(C.City,"") = COALESCE(@City,C.City,"") 

更多關於此功能here

Answer 3

CREATE PROCEDURE [dbo].[SearchCustomer] 
@FirstName varchar(30) --REQUIRED 
@LastName varchar(30)--REQUIRED 
@City varchar(30) --OPTIONAL 
AS 

IF @City is NULL 
BEGIN 
SELECT * FROM CUSTOMER C WHERE 
C.FirstName = @FirstName AND 
C.LastName = @LastName 
END 
ELSE 
BEGIN 
SELECT * FROM CUSTOMER C WHERE 
C.FirstName = @FirstName AND 
C.LastName = @LastName AND 
C.City = @City 
END