SQL用值列表替换null

Question

我有一个City和StatePopulation表

CREATE TABLE dbo.City 
(
     Code INT, 
     CityName VARCHAR(30)
)

INSERT INTO CITY (CODE, CityName)
   select 1, 'Woodside'
   union
   select 2, 'Sunnyside'
   union
   select 3, 'Flushing'
   union
   select 4, 'Elmhurst'
   union
   select 5, 'ForestHills'
   union
   select 6, 'Manhattan'
   union
   select 7, 'Atlanta'
   union
   select 8, 'Alpharetta'
   union
   select 9, 'Johns Creek'

CREATE TABLE DBO.CityPopulation 
(
     StateCode VARCHAR(10), 
     CityCode INT, 
     PopulationCount INT
)

INSERT INTO DBO.CityPopulation (StateCode, CityCode, PopulationCount)
   SELECT 'NY', 1, 1000
   UNION
   SELECT 'NY', 2, 1500
   UNION
   SELECT 'NY', 3, 2500
   UNION
   SELECT 'NY', 4, 3000
   UNION
   SELECT 'NY', 5, 3500
   UNION
   SELECT 'NY', 6, 4000
   UNION
   SELECT 'GA', 7, 5500
   UNION
   SELECT 'GA', 8, 1200
   UNION
   SELECT 'GA', 9, 1900

CREATE TYPE dbo.UDTT_StateType AS TABLE (StateCode VARCHAR(10), CityCode INT)

DECLAR @State dbo.UDTT_StateType

INSERT INTO @State (StateCode, CityCode)
   select 'NY', null
   union
   select 'GA', 8

现在，我需要返回CityPopulation中UDTT_StateType和StateCode上匹配的CityCode中的值的行，但是当{{1} }为'NY'，而StateCode为空，我需要返回CityCode 1和2的数据

请问有人可以帮我写这个查询吗？

Answer 1

我能够通过CROSS JOIN解决这个问题。

SELECT cpd.StateCode, cpd.CityCode, cpd.CityName, cpd.PopulationCount 
FROM @State AS s 
CROSS JOIN (SELECT * FROM CityPopulation AS cp INNER JOIN city AS c ON cp.CityCode = c.Code 
                WHERE CityCode IN (1,2)) AS cpd 
WHERE s.CityCode = cpd.CityCode OR s.CityCode IS NULL

产生以下结果：

Answer 2

您可以尝试这个；

select c.* from CityPopulation c,@State s where 
s.CityCode is null
And c.CityCode  in (1,2,3,4,5,6)                
And c.StateCode = s.StateCode
 Union 
select c.* from CityPopulation c,@State s where 
c.CityCode  =s.CityCode                
And c.StateCode = s.StateCode

Answer 3

select c.*
from CityPopulation c, State s
where (
  (c.StateCode = s.StateCode and c.CityCode = s.CityCode)
  OR (s.StateCode = 'NY' and s.CityCode is null and (c.StateCode='NY' and c.CityCode in (1,2)))
)