Python查詢 - 網絡應用程序等

Question

def get_songs(requested_username): 
    songs = db.GqlQuery("SELECT * FROM Song ORDER BY created DESC") 

Song db.Model實體具有username屬性。

如何找到只有一個特定用戶名的所有歌曲，如果歌曲的用戶名屬性等於請求的用戶名？

Answer 1

你可以做到這一點有兩種方式：

GQL

def get_songs(requested_username): 
    songs = db.GqlQuery('SELECT * FROM Song WHERE username=:1 ORDER BY created DESC', requested_username) 
    return songs 

查詢實例：

def get_songs(requested_username): 
    songs = Song.all() 
    songs.filter('username =', requested_username).order('-created') 
    return songs 

在這兩種情況下，songs都將包含查詢結果，您可以遍歷它並根據需要訪問裏面的對象。

songs = get_songs(requested_username) 
for song in songs: 
    # Do stuff here... 

Answer 2

像

SELECT * FROM Song where username="Batman" ORDER BY created DESC 

你可能不希望使用蝙蝠俠在這種情況下

Answer 3

建議你檢查出的文檔 - >https://developers.google.com/appengine/docs/python/datastore/queries#Filters

但是，爲了回答你的問題，這樣的事情：

def get_songs(requested_username, limit=10): 
    query = db.GqlQuery("SELECT * FROM Song WHERE username = :1 ORDER BY created DESC", requested_username) 
    songs = query.fetch(limit) 
    return songs