如何在TSQL中創建布爾計算字段並加入該計算字段？

Question

首先看看這段代碼。 我覺得它應該適合我，但事實並非如此！ （驚喜！）

無論如何，這是我首先嘗試的：

SELECT
Status as status,
Address as ip,
PCName as pc_name,
(Numbers.Phone = 'CPU/' + PCName) as cpu_contact,
(Numbers.Phone = 'PC/' + PCName) as pc_contact,
(Numbers.Phone = 'LOGIN/' + PCName) as login_contact,
FROM IPAddress
WHERE $where  --Generated In code
JOIN Numbers
  ON ('CPU/' + PCName = Numbers.Phone) 
  OR ('PC/' + PCName = Numbers.Phone) 
  OR ('LOGIN/' + PCName = Numbers.Phone)

所以我想要的是一些布爾計算字段並在類似條件下加入。 我還希望結果可以折疊成單行。 例如，我認為當前的設置會做這樣的事情：

status ip  cpu_contact pc_contact login_contact
-----------------------------------------------
foo    bar true        false      false
foo    bar false       true       false
foo    bar false       false      true

顯然我寧願

status ip  cpu_contact pc_contact login_contact
-----------------------------------------------
foo    bar true        true       true

有任何想法嗎？ 數據庫重新設計不是一種選擇。 如果是的話，我會這樣做:-)

Answer 1

您可以使用GROUP BY和SUM來折疊行：

SELECT
  Status as status, Address as ip, PCName as pc_name,
  cast(sum(case when (Numbers.Phone = 'CPU/' + PCName) then 1 else 0 end) as bit)
    as cpu_contact,
  cast(sum(case when (Numbers.Phone = 'PC/' + PCName) then 1 else 0 end)) as bit)
    as pc_contact,
  cast(sum(case when (Numbers.Phone = 'LOGIN/' + PCName) then 1 else 0 end) as bit)
    as login_contact,
FROM
  IPAddress
    JOIN Numbers ON 
      ('CPU/' + PCName = Numbers.Phone) OR ('PC/' + PCName = Numbers.Phone) OR 
      ('LOGIN/' + PCName = Numbers.Phone)
WHERE
  $where  --Generated In code
GROUP BY
  Status, Address, PCName

由於您正在執行邏輯或行之間，因此零之和為false，而大於0的任何值都為true。

Answer 2

您需要使用Case / When進行比較。 在這種情況下，我硬編碼1或0，但T-SQL會將硬編碼的數字轉換為int。 如果你想要布爾（位），你需要手動轉換，就像這樣......

Convert(Bit, Case When Numbers.Phone = 'CPU/' + PCName Then 1 Else 0 End) as cpu_contact,
Convert(Bit, Case When Numbers.Phone = 'PC/' + PCName Then 1 Else 0 End) as pc_contact,
Convert(Bit, Case When Numbers.Phone = 'LOGIN/' + PCName Then 1 Else 0 End) as login_contact,

Answer 3

SELECT
Status as status,
Address as ip,
PCName as pc_name,
case when sum(case when Numbers.Phone = 'CPU/' + PCName then 1 end) > 0 then 'true' else 'false' end as cpu_contact,
case when sum(case when Numbers.Phone = 'PC/' + PCName then 1 end) > 0 then 'true' else 'false' end as pc_contact,
case when sum(case when Numbers.Phone = 'LOGIN/' + PCName then 1 end) > 0 then 'true' else 'false' end as login_contact
FROM IPAddress
JOIN Numbers
  ON ('CPU/' + PCName = Numbers.Phone) 
  OR ('PC/' + PCName = Numbers.Phone) 
  OR ('LOGIN/' + PCName = Numbers.Phone)
WHERE -- your condition goes here
group by status, address, pc_name