[英]mySQL two COUNTS in one query with 3 tables involved
我有3張桌子,即:Town; 村; 農民...我需要計算每個村庄有多少個農民,以及每個鎮有多少個村庄。 我是php和mysql的新手,所以我的代碼仍然很垃圾。.到目前為止,我已經完成了查詢代碼:
$query = "SELECT *, COUNT(DISTINCT village.villageID) AS cnt_village,
COUNT( farmer.farmerID ) AS cnt_farmers
FROM town LEFT JOIN village ON village.townID = town.townID
LEFT JOIN farmer ON farmer.villageID = village.villageID
GROUP BY town.townID
ORDER BY town.townName";
$result = mysql_query($query);
它已經輸出了正確的計數,如下所示:
----TOWN--------VILLAGES----FARMERS-----
| Caibiran | 2 | 23 |
| Culaba | 7 | 39 |
| TOTAL | 9 | 62 |
直到我嘗試搜索特定城鎮之前,它都能正常工作。 發生的情況是“農民”列的值顯示了指定鎮的正確值。 但是整個表格仍然顯示,其他城鎮的農民列顯示0。
它顯示了這一點:
----TOWN--------VILLAGES----FARMERS-----
| Caibiran | 2 | 23 |
| Culaba | 7 | 0 |
| TOTAL | 9 | 23 |
但是我真正想要的是:
----TOWN--------VILLAGES----FARMERS-----
| Caibiran | 2 | 23 |
| TOTAL | 2 | 23 |
但是我不知道該怎么做。 而且我的想法已經用光了。 請幫我。
這樣可以解決問題嗎?
SELECT *, COUNT(DISTINCT village.villageID) AS cnt_village,
COUNT( farmer.farmerID ) AS cnt_farmers
FROM town
JOIN village ON village.townID = town.townID
JOIN farmer ON farmer.villageID = village.villageID
GROUP BY town.townID
ORDER BY town.townName
由於將沒有任何農民可以加入,因此應將行從結果集中刪除。
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