問題的別名加入statiment

我有以下查詢的問題：問題的別名加入statiment

SELECT 
    g_contac.contid, g_contac.name, g_contac.email, f_sync.foreign_key, 
    (
     SELECT COUNT(g_cpers.cpersid) 
     FROM g_cpers 
     WHERE g_cpers.contid = g_contac.contid 
    ) AS employee_count 
FROM f_sync 
    FULL OUTER JOIN g_contac ON 
    (
     g_contac.contid = f_sync.external_id AND 
     model = case when f_sync.employee_count = 0 then 'PRIVATE' else 'COMPANY' end 
    ) 
WHERE model = 'COMPANY' or model = 'PRIVATE' OR model IS null

當我執行它，我得到錯誤：

無效的列名稱employee_count「。

如何解決這個問題？

來源

2011-06-02 Dusan

在聯接語句中定義的模型上的where子句不會導致選擇所有行嗎？ – 2011-06-02 08:04:07

你在f_sync表中有employee_count字段嗎？如果不是，那麼錯誤是正確的。 – Arvo 2011-06-02 08:13:54

@Arvo：我沒有。我從內部select中選擇 – Dusan 2011-06-02 08:15:21

那是因爲你在查詢中提到f_sync.employee_count，但f_sync沒有列名爲employee_count：您剛纔創建的查詢中的動態列與別名employee_count。

簡單的解決方法是重複計算：

SELECT 
g_contac.contid, g_contac.name, g_contac.email, f_sync.foreign_key, 
(
    SELECT COUNT(g_cpers.cpersid) 
    FROM g_cpers 
    WHERE g_cpers.contid = g_contac.contid 
) AS employee_count 
FROM f_sync 
FULL OUTER JOIN g_contac ON 
(
    g_contac.contid = f_sync.external_id AND 
    model = case when (SELECT COUNT(g_cpers.cpersid) 
    FROM g_cpers 
    WHERE g_cpers.contid = g_contac.contid) = 0 then 'PRIVATE' else 'COMPANY' end 
) 
WHERE model = 'COMPANY' or model = 'PRIVATE' OR model IS null;

更好的解決方法是創建包括該列，這意味着它只能進行一次計算的圖。

編輯：改進的查詢和彙集各方意見

您可以通過使用SQL not exists而不是count(*) = 0提高清晰度一點：

SELECT 
g_contac.contid, g_contac.name, g_contac.email, f_sync.foreign_key 
FROM f_sync 
FULL OUTER JOIN g_contac ON 
(
    g_contac.contid = f_sync.external_id AND 
    model = case when not exists (SELECT * FROM g_cpers 
     WHERE g_cpers.contid = g_contac.contid) then 'PRIVATE' else 'COMPANY' end 
) 
WHERE model = 'COMPANY' or model = 'PRIVATE' OR model IS null;

來源

2011-06-02 08:15:11 Bohemian

謝謝，這是我需要的。注意：您可以刪除（ SELECT COUNT（g_cpers.cpersid） FROM g_cpers WHERE g_cpers.contid = g_contac.contid ）AS employee_count from code – Dusan 2011-06-02 08:32:49

你能試試這個：

SELECT 
    gt.contid, gt.name, gt.email, f_sync.foreign_key, 
    gt.employee_count 
FROM f_sync 
    FULL OUTER JOIN 
    ( SELECT 
      g_contac.contid, g_contac.name, g_contac.email, 
      (
       SELECT COUNT(g_cpers.cpersid) 
       FROM g_cpers 
       WHERE g_cpers.contid = g_contac.contid 
      ) AS employee_count 
     FROM g_contac 
    ) AS gt ON 
    (
     gt.contid = f_sync.external_id AND 
     model = case when gt.employee_count = 0 then 'PRIVATE' else 'COMPANY' end 
    )

來源

2011-06-02 08:15:24

問題的別名加入statiment

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