查詢：加入，Concat的，但得到的結果

Question

您好，

我在這裏有一個問題。我正在尋找一個搜索選項。我可以搜索名字，姓氏，公司名稱和編號。我只想顯示左側和客戶信息，這些信息是通過以下查詢獲得的。但是，如果客戶沒有標牌，則不會顯示客戶。有沒有辦法阻止？

SELECT DISTINCT A.* 
FROM adressen AS A 
OUTER JOIN fahrzeuge AS F 
ON F.fa_kunden_id = A.ad_id 
WHERE CONCAT(coalesce(A.ad_name), coalesce(A.ad_vorname),coalesce(A.ad_firma), coalesce(F.fa_kennzeichen)) LIKE '%"+wndHauptfenster.textfield_suche.Text+"%' 

我使用IFNULL過，但是，這會導致 '無結果' 試過了，甚至爲客戶提供汽車：

SELECT DISTINCT A.* 
FROM adressen AS A 
OUTER JOIN fahrzeuge AS F 
ON F.fa_kunden_id = A.ad_id 
WHERE CONCAT(coalesce(A.ad_name), coalesce(A.ad_vorname),coalesce(A.ad_firma), coalesce(ifnull(F.fa_kennzeichen, 'leer'))) LIKE '%"+wndHauptfenster.textfield_suche.Text+"%' 

UPDATE：試圖給定的解決方案後，它根本找不到任何東西。

SELECT DISTINCT A.* 
FROM adressen AS A 
OUTER JOIN fahrzeuge AS F 
ON F.fa_kunden_id = A.ad_id 
WHERE CONCAT(coalesce(A.ad_name, ''), coalesce(A.ad_vorname, ''),coalesce(A.ad_firma, ''), coalesce(F.fa_kennzeichen, '')) LIKE '%"+wndHauptfenster.textfield_suche.Text+"%' 

在Adressen列：

• ad_vorname包含Max
• ad_name包含Mustermann
• ad_firma包含Testfirma Inc
• fa_kennzeichen包含什麼。查詢正在搜索的行不存在。

Answer 1

如何：

SELECT DISTINCT A.* 
FROM adressen AS A 
OUTER JOIN fahrzeuge AS F 
ON F.fa_kunden_id = A.ad_id 
WHERE CONCAT(coalesce(A.ad_name,''), coalesce(A.ad_vorname,''),coalesce(A.ad_firma,''), coalesce(F.fa_kennzeichen,'')) LIKE '%"+wndHauptfenster.textfield_suche.Text+"%' 

Answer 2

OUTER JOIN是一個語法錯誤。應該是LEFT OUTER JOIN，或縮寫爲LEFT JOIN。

SELECT DISTINCT A.* 
FROM adressen AS A 
LEFT OUTER JOIN fahrzeuge AS F 
ON F.fa_kunden_id = A.ad_id 
WHERE CONCAT(coalesce(A.ad_name, ''), coalesce(A.ad_vorname, ''),coalesce(A.ad_firma, ''), coalesce(F.fa_kennzeichen, '')) LIKE '%"+wndHauptfenster.textfield_suche.Text+"%'