將同一個表上的多個MySQL查詢合併爲一個

Question

如何在同一個表上進行多個查詢，選擇不同的列？

如果它有幫助......所有查詢在SQL語句的選擇部分都有一個共同的列。他們都選擇了ID，然後是特定的東西。

因此，每個查詢需要ID和以下任一項：post_name,post_title或post_excerpt。

此外，如果它有助於簡化事情。我正在嘗試在這些列中搜索廣泛匹配項和精確匹配項。

所以在我的示例中，我將查找：「floor finish」，「floor」或「finish」在以下列中：post_name,post_title和post_excerpt。全部在同一張表內。

我試圖用UNION來實現這個。

這裏是我的查詢：

Array 
(
    [broad] => Array 
     (
      [floor] => Array 
       (
        [slugs] => SELECT `ID`, `post_name` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_name` LIKE '%floor%' 
        [titles] => SELECT `ID`, `post_title` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_title` LIKE '%floor%' 
        [excerpts] => SELECT `ID`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_excerpt` LIKE '%floor%' 
       ) 

      [finish] => Array 
       (
        [slugs] => SELECT `ID`, `post_name` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_name` LIKE '%finish%' 
        [titles] => SELECT `ID`, `post_title` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_title` LIKE '%finish%' 
        [excerpts] => SELECT `ID`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_excerpt` LIKE '%finish%' 
       ) 

     ) 

    [exact] => Array 
     (
      [slugs] => SELECT `ID`, `post_name` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_name` LIKE '%floor-finish%' 
      [titles] => SELECT `ID`, `post_title` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_title` LIKE '%floor finish%' 
      [excerpts] => SELECT `ID`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_excerpt` LIKE '%floor finish%' 
     ) 

    [combined] => (SELECT `ID`, `post_name` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_name` LIKE '%floor-finish%') UNION (SELECT `ID`, `post_name` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_name` LIKE '%floor%') UNION (SELECT `ID`, `post_name` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_name` LIKE '%finish%') UNION (SELECT `ID`, `post_title` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_title` LIKE '%floor finish%') UNION (SELECT `ID`, `post_title` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_title` LIKE '%floor%') UNION (SELECT `ID`, `post_title` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_title` LIKE '%finish%') UNION (SELECT `ID`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_excerpt` LIKE '%floor finish%') UNION (SELECT `ID`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_excerpt` LIKE '%floor%') UNION (SELECT `ID`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_excerpt` LIKE '%finish%') 
) 

然而，上述結果是有趣的。我似乎得到所有正確的結果，除了每個結果值（應該是列的名稱）的關鍵字始終保持不變。即使分配給它的值可能是post_title或post_excerpt，它始終爲post_name。

所以每個結果都有一個ID和post_name。基本上他們的鑰匙是錯的，但是這些數值似乎是準確的。

我也嘗試過這樣的事情：

Array 
     (
      [broad] => Array 
       (
        [floor] => SELECT `ID`, `post_name`, `post_title`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND (`post_name` LIKE '%floor%' OR `post_title` LIKE '%floor%' OR `post_excerpt` LIKE '%floor') 
        [finish] => SELECT `ID`, `post_name`, `post_title`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND (`post_name` LIKE '%finish%' OR `post_title` LIKE '%finish%' OR `post_excerpt` LIKE '%finish%') 
       ) 

      [exact] => SELECT `ID`, `post_name`, `post_title`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND (`post_name` LIKE '%floor-finish%' OR `post_title` LIKE '%floor finish%' OR `post_excerpt` LIKE '%floor finish%') 
      [combined] => SELECT `ID`, `post_name`, `post_title`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND (`post_name` LIKE '%floor-finish%' OR `post_title` LIKE '%floor finish%' OR `post_excerpt` LIKE '%floor finish%') UNION (SELECT `ID`, `post_name`, `post_title`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND (`post_name` LIKE '%floor%' OR `post_title` LIKE '%floor%' OR `post_excerpt` LIKE '%floor%')) UNION (SELECT `ID`, `post_name`, `post_title`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND (`post_name` LIKE '%finish%' OR `post_title` LIKE '%finish%' OR `post_excerpt` LIKE '%finish%')) 
     ) 

) 

這是沿着什麼，我試圖完成的線條更。我希望每個結果都有ID,post_excerpt,post_slug和post_title。如果沒有匹配，則顯示它們的鍵值爲空，或者完全不顯示該鍵。

第二次嘗試的問題是，它只需要三個所需列中的一個匹配。因此，如果它匹配post_excerpt而沒有其他地方，它仍然會從post_title和post_name中提取值。從而導致結果不準確。

我已經閱讀了幾個似乎是類似的問題，但大多數都沒有真正明確的答案......或者...問題/答案更適合於SEPARATE表上的多個查詢。

關於在同一個表上組合多個MySQL查詢的任何指導或建議？

BY THE WAY ...我在我的例子中使用「組合」作爲我的最終查詢發送到數據庫。

所以再一次......如果列中沒有匹配，則顯示它們爲空或完全忽略結果中的鍵。

Answer 1

由於查詢中的UNION語句，您得到錯誤的「密鑰」。您有不同的鍵名稱，但是三個不同列之間的兼容列類型是聯合查詢。而不是拋出一個錯誤，數據庫引擎剛剛從第一個查詢選擇列名和使用，對所有的人：

id | post_name # <= column name in first query 
1 | "my post" 

UNION 

id | post_title # <= column name is different, but type is compatible, so UNION succeeds 
1 | "my post title" 

UNION 

id | post_excerpt # <= ditto 
1 | "my post excerpt" 

會導致：

id | post_name # <= column name from first query 
1 | "my post" 
1 | "my post title" 
1 | "my post excerpt" 

這是你是什麼經歷。

相反，你可以這樣做：

id | post_name | post_title | post_excerpt 
1 | "my post" | null  | null  # <= deliberately select nulls for these columns in this query 

UNION 

id | post_name | post_title  | post_excerpt 
1 | null  | "my post title" | null 

UNION 

id | post_name | post_title | post_excerpt 
1 | null  | null  | "my post excerpt" 

這將使你類似的結果：

id | post_name | post_title  | post_excerpt 
1 | "my post" | null   | null 
1 | null  | "my post title" | null 
1 | null  | null   | "my post excerpt" 

隨着你的表中，這是一個非常基本的版本可能看起來像：

SELECT ID, post_name, null AS post_title, null AS post_excerpt FROM tps_3_posts 

UNION 

SELECT ID, null AS post_name, post_title, null AS post_excerpt FROM tps_3_posts 

UNION 

SELECT ID, null AS post_name, null AS post_title, post_excerpt FROM tps_3_posts 

這可能更適用於您正在嘗試做的事情。 Here's a SQLFiddle如果你想看到它的行動。

Answer 2

正如我在第二種情況下所理解的那樣，問題是隻有匹配的列應該有值，而其他的應該爲空。對於這種情況，您可以在SELECT中使用IF/ELSE或WHEN語句。這個想法是你選擇的實際值是該列對應於期望值的值，否則爲null。

另一個可能的解決方案是你可以編寫例如

SELECT `ID`, `post_name`, `post_title`, 'post_excerpt' 

因此，您選擇WHERE語句中條件的字符串值，稍後可以使用該值來了解該行屬於哪個屬性。