避免重複數據PostgreSQL

只有在數據庫中存在does not時，我如何將這些artist插入到數據庫中。我寫了下面的代碼。但這是錯誤的。你能幫我嗎？感謝避免重複數據PostgreSQL

藝術家名單

Lata Mangeshkar 
Lata Mangeshkar 
Lata Mangeshkar 
Asha Bhosle 
Lata Mangeshkar 
Mahendra Kapoor 
Lata Mangeshkar 
Kishore Kumar 
Lata Mangeshkar

我的代碼

for l in artist: 
     l = l.strip() 
     cursor.execute("SELECT id FROM song_artist WHERE name = %s ;" ,(l,)) # Id exist? 
     artist_rows = cursor.fetchone() 
     if not artist_rows: 
      artist_slug = self.makeSlug(artist[0]) 
      cursor.execute('INSERT INTO song_artist (name,slug) VALUES (%s,%s) RETURNING id;',(artist[0],artist_slug)) 
      print k

輸出：

INSERT INTO song_artist (name,slug) VALUES (Lata Mangeshkar,lata-mangeshkar) RET 
URNING id; 
INSERT INTO song_artist (name,slug) VALUES (Lata Mangeshkar,lata-mangeshkar) RET 
URNING id; 
INSERT INTO song_artist (name,slug) VALUES (Lata Mangeshkar,lata-mangeshkar) RET 
URNING id; 
INSERT INTO song_artist (name,slug) VALUES (Lata Mangeshkar,lata-mangeshkar) RET 
URNING id; 
INSERT INTO song_artist (name,slug) VALUES (Asha Bhosle,asha-bhosle) RETURNING i 
d; 
INSERT INTO song_artist (name,slug) VALUES (Lata Mangeshkar,lata-mangeshkar) RET 
URNING id; 
INSERT INTO song_artist (name,slug) VALUES (Mahendra Kapoor,mahendra-kapoor) RET 
URNING id; 
INSERT INTO song_artist (name,slug) VALUES (Mahendra Kapoor,mahendra-kapoor) RET 
URNING id; 
INSERT INTO song_artist (name,slug) VALUES (Lata Mangeshkar,lata-mangeshkar) RET 
URNING id;

輸出應爲：

INSERT INTO song_artist (name,slug) VALUES (Asha Bhosle,asha-bhosle) RETURNING i 
d; 
INSERT INTO song_artist (name,slug) VALUES (Lata Mangeshkar,lata-mangeshkar) RET 
URNING id; 
INSERT INTO song_artist (name,slug) VALUES (Mahendra Kapoor,mahendra-kapoor) RET 
URNING id;

更新：

我已經添加了對列名的約束來強制該列是唯一的。

來源

2011-11-22 Kulbir

你必須使用if not artist_rows:這是全部

artist_slug = self.makeSlug(l) 

cursor.execute("SELECT count(id) FROM song_artist WHERE name = %s and slug = %s ;" ,(l,artist_slug)) # Id exist? 
artist_rows = cursor.fetchone() 
#artist_rows = artist_rows[0] 
db.commit() 
if not artist_rows: 
cursor.execute('INSERT INTO song_artist (name,slug) VALUES (%s,%s) RETURNING id;',(l,artist_slug)) 
#k=('INSERT INTO song_artist (name,slug) SELECT %s,%s WHERE NOT EXISTS (SELECT 42 FROM song_artist WHERE name = %s) RETURNING id;'%(l,artist_slug,l)) 
artist_id = cursor.fetchone()[0] # get mysql_insert_id using RETURNING 
db.commit()

來源

2011-11-23 07:36:20

強制在數據庫端。在列名上添加約束以強制該列是唯一的。這應該足夠了：

ALTER TABLE song_artist ADD UNIQUE（name）;

這樣你就可以確定無論你做什麼，你都不會有任何重複的值。
你可以插入使用查詢這樣的數據：

INSERT INTO song_artist（名稱，蛞蝓）
SELECT '馬亨德拉·卡普爾'，「馬亨德拉 - 卡普爾
WHERE NOT EXISTS
（
SELECT 42
FROM song_artist
WHERE name ='Mahendra Kapoor'
）;

來源

2011-11-22 14:19:56

這是com折襞。什麼是42？ – Kulbir

我試過你的代碼。但不工作。獲取錯誤消息。 'psycopg2.IntegrityError：重複鍵值違反唯一約束「song_ar tist_slug_key」詳細信息：鍵（slug）=（lata-mangeshkar）已存在。「＃ – Kulbir

這是因爲您已經有重複的數據。刪除重複項並重試。 –

您可以添加唯一的約束作爲Szymon GUZ建議，

ALTER TABLE song_artist ADD UNIQUE (name);

然後使用try/except來處理重複的錯誤：

try: 
    cursor.execute('INSERT INTO song_artist (name,slug) VALUES (%s,%s) RETURNING id;',(artist[0],artist_slug)) 

except psycopg2.IntegrityError: 
    debug.print 'Duplicate values found. Insert was not successful'

來源

2011-11-22 19:21:39 vasek1

避免重複數據PostgreSQL

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