閱讀從MySQL數據庫

Question

評估數據我有一個MySQL數據庫表具有以下colums

ID 
status (can contain values 0, 1, 2) 
timepstamp 
text 
note 
owner 

我想獲得關於非特異性老闆從表中的條目下列信息：

number of entries 
number of entries where status=0 
number of entries where status=1 
number of entries where status=2 
number of entries where LENGTH(note)>0 
minimum timestamp 
maximum timestamp 

我用來讀取完整的數據集，然後使用

SELECT status, timestamp, LENGTH(note)>0 WHERE owner="name"; 

我用PHP對其進行評估有一些用戶有這麼多條目的問題，以至於如果我將數據讀取到PHP中，我經常會遇到內存不足錯誤。我認爲讓MySQL評估數據應該更具性能。我無法寫出能夠完成此任務的查詢。

SELECT 
    MIN(timestamp) AS mintime, 
    MAX(timestamp) AS maxtime, 
    COUNT(*) AS number, 
    ... 
WHERE owner="name" 

難道在某種程度上可以一次獲得結果嗎？例如用嵌套的WHERE或IF內的COUNT？

COUNT(WHERE status=0) AS inactive 
    COUNT(IF(status=1)) AS active 
    ... 

你會如何解決這個問題？

Answer 1

這給一個嘗試 -

SELECT 
    COUNT(*) AS total, 
    SUM(IF(status=0, 1, 0)) AS stat0, 
    SUM(IF(status=1, 1, 0)) AS stat1, 
    SUM(IF(status=2, 1, 0)) AS stat2, 
    SUM(IF(LENGTH(note)>0, 1, 0)) AS notes, 
    MIN(timestamp) AS mintime, 
    MAX(timestamp) AS maxtime 
FROM tbl_name 
WHERE owner="name" 
GROUP BY owner 

Answer 2

試試這個：

SELECT 
MIN(`timestamp`) AS `mintime`, 
MAX(`timestamp`) AS `maxtime`, 
COUNT(`ID`) AS `number`, 
(SELECT COUNT(`ID`) FROM `Table` WHERE `owner` = 'owner' AND `status` = 0) AS `inactive`, 
(SELECT COUNT(`ID`) FROM `Table` WHERE `owner` = 'owner' AND `status` = 1) AS `active`, 
(SELECT COUNT(`ID`) FROM `Table` WHERE `owner` = 'owner' AND LENGTH(`note`)>0) AS `longentries` 
FROM `Table` 
WHERE `owner` = 'name' 

你或許應該考慮規範化數據庫設計，不過，這樣你將有兩個單獨的表，一個是用戶和一個條目，像這樣：

USERS ID 名 狀態

個

參賽作品 ID user_ID的 時間戳 文本 說明（如果這是一個特定的入口域;否則將它移動到桌面上）用戶名：密碼：

希望這會有所幫助。