如何判斷一個sqlite3的數據庫中存在的值，蟒蛇

Question

如何判斷一個sqlite3的數據庫中存在的值，蟒蛇

這是到目前爲止我的代碼：

def signup(): 
    email = request.form['email'] 
    username = request.form['user'] 
    password = request.form['password'] 
    g.db.execute("INSERT INTO users VALUES (?, ?, ?)", [email, username, password]) 
    g.db.commit() 

我想它只能將值插入到數據庫中，如果email和username不在數據庫中，但我不知道從哪裏開始。

Answer 1

您只需在插入前進行查詢，然後執行fetchone即可。如果fetchone回報的東西，那麼你肯定知道，有一個記錄已經在具有email或username的DB：

def signup(): 
    email = request.form['email'] 
    username = request.form['user'] 
    password = request.form['password'] 

    # Create cursor object 
    cur = g.db.cursor() 

    # run a select query against the table to see if any record exists 
    # that has the email or username 
    cur.execute("""SELECT email 
          ,username 
        FROM users 
        WHERE email=? 
         OR username=?""", 
       (email, username)) 

    # Fetch one result from the query because it 
    # doesn't matter how many records are returned. 
    # If it returns just one result, then you know 
    # that a record already exists in the table. 
    # If no results are pulled from the query, then 
    # fetchone will return None. 
    result = cur.fetchone() 

    if result: 
     # Record already exists 
     # Do something that tells the user that email/user handle already exists 
    else: 
     cur.execute("INSERT INTO users VALUES (?, ?, ?)", (email, username, password)) 
     g.db.commit()