使用連接和「幽靈」引用優化postrgeSQL查詢？

Question

我做了這個查詢來獲取一些數據。

select th.id, th.ticket_id, tp.name AS priority, ts.name AS state, owner_id AS player_id, g.id AS team_id, tt.name AS ticket_type 
from ticket_history th, ticket_priority tp, ticket_state ts, users, queue, ticket_type tt, groups g 
where th.priority_id = tp.id 
AND queue.id = g.id 
AND th.state_id = ts.id 
AND owner_id = users.id 
AND th.queue_id = queue.id 
AND th.type_id = tt.id 
AND th.id > $lastUpdateId 
ORDER BY th.id desc 

它工作得很好，但我得到了一些抱怨說，這個查詢很慢（以下簡稱「投訴人」甚至沒有到，雖然測試）...但我決定與一些內部連接調整它 - 第一個問題：這是連接表的最有效方式，並避免重複主ID（在這種情況下，ticket_history）正確嗎？

我重構查詢看起來像這樣：

select th.id, th.ticket_id, tp.name AS priority, ts.name AS state, owner_id AS player_id, g.id AS team_id, tt.name AS ticket_type 
FROM ticket_history, groups 
INNER JOIN queue ON queue.id = groups.id 
INNER JOIN ticket_priority ON ticket_priority.id = ticket_history.priority_id 
INNER JOIN ticket_state ON ticket_state.id = ticket_history.state_id 
INNER JOIN users ON users.id = ticket_history.owner_id 
INNER JOIN queue ON queue.id = ticket_history.queue_id 
INNER JOIN ticket_type ON ticket_type.id = ticket_history.type_id 
WHERE th.id > 7352616 
ORDER BY th.id desc 

，但現在我得到這讓我想起我的第二個問題的錯誤

ERROR: invalid reference to FROM-clause entry for table "ticket_history" 
LINE 4: ...NER JOIN ticket_priority ON (ticket_priority.id = ticket_his... 
                  ^
HINT: There is an entry for table "ticket_history", but it cannot be referenced from this part of the query. 
********** Error ********** 

ERROR: invalid reference to FROM-clause entry for table "ticket_history" 
SQL state: 42P01 
Hint: There is an entry for table "ticket_history", but it cannot be referenced from this part of the query. 

- 這是什麼意思？我需要引用ticket_history.priority_id ...

PS：我的目標是獲取ticket_history中的數據，但不是擁有priority_id，而是需要實際的優先級文本等等（除了用戶和組我實際上想要他們的ID而不是名稱）。最棘手的部分是我在ticket_history中有一個隊列ID，我需要從隊列表中提取我實際需要的group_id。

編輯：這裏是從第一個查詢

id; ticket_id; priority; state; user_id; group_id; type  
7376618; 203123; "4 Low"; "closed"; 385; 22; "Service Request" 
7376617; 201341; "3 Medium"; "closed"; 100; 21; "Problem" 
7376616; 2; "1 SuperDuperHigh"; "closed"; 150; 10; "Service Request" 

該查詢從本地主機實例返回19067秒（給予或採取）7360行的示例結果。 原始表「原樣」包含id而不是文本/數字。所以它包含「type_id」而不是類型。 group_id是從兩個不同表格之間的關聯中提取的。它去ticket_history-> queue->組因此它需要涉及這些ID的找到GROUP_ID

EDIT2：提供的圖表看起來像這樣（link） - 查找周邊的票表 - 這是最大的一個，你可以看到

Answer 1

我想你不能在那裏引用ticket_history，因爲你在ticket_history和groups之間有逗號，所以ticket_history不是所有這些內部連接的一部分。如果我理解正確你的表結構[如果你發佈的表DEFS和樣本數據會更容易BTW]我認爲這將工作：

select th.id, th.ticket_id, tp.name AS priority, ts.name AS state, owner_id AS player_id, g.id AS team_id, tt.name AS ticket_type 
FROM groups 
INNER JOIN queue ON queue.id = groups.id 
-- include ticket_history with a join statement 
INNER JOIN ticket_history ON queue.id = ticket_history.queue_id 
    INNER JOIN ticket_priority ON ticket_priority.id = 
ticket_history.priority_id 
INNER JOIN ticket_state ON ticket_state.id = ticket_history.state_id 
INNER JOIN users ON users.id = ticket_history.owner_id 

INNER JOIN ticket_type ON ticket_type.id = ticket_history.type_id 
WHERE th.id > 7352616 
ORDER BY th.id desc 

Answer 2

從documentation：

連接子句結合了兩個FROM項目，爲了方便起見，我們將 稱爲「表格」，儘管實際上它們可以是任何類型的FROM 項目。如有必要，使用括號來確定嵌套的順序。 在沒有括號的情況下，JOIN從左到右嵌套。 無論如何 JOIN綁定比分隔FROM列表項目的逗號更緊密。

因此，連續的JOIN是相對於「組」而不是「ticket_history」。翻轉表的順序，使其工作：

SELECT th.id, th.ticket_id, tp.name AS priority, ts.name AS state, owner_id AS player_id, 
     g.id AS team_id, tt.name AS ticket_type 
FROM ticket_history th 
JOIN ticket_priority tp ON tp.id = th.priority_id 
JOIN ticket_state ts ON ts.id = th.state_id 
-- JOIN users ON users.id = th.owner_id NOT USED IN THE QUERY 
JOIN queue ON queue.id = th.queue_id 
JOIN ticket_type tt ON tt.id = th.type_id 
JOIN groups g ON g.id = queue.id 
WHERE th.id > 7352616 
ORDER BY th.id DESC; 

注意INNERJOIN之前是沒有用的字;你可以放心地省略它。