使用 SQL 数据表建立索引

Question

我创建了一个数据库，用作时令水果/蔬菜列表。我需要使用用户输入搜索该数据库，然后将其附加到一个空列表，然后附加该输入中的价格值，并将其附加到第二个空列表。但是，当我运行该程序时，它会读取 IndexError：列表索引超出范围。

之后我需要做的是要求用户输入他们想要选择的商品的公斤数，然后乘以价格（我应该从索引中获得）。

import sqlite3
connection = sqlite3.connect('seasonalProduce.db')
cursor = connection.cursor()
cursor.execute("""CREATE TABLE IF NOT EXISTS productList (
     productID INTEGER PRIMARY KEY,
     productName text NOT NULL,
     productPrice real
);""")



#add rows (records) to the productList table

productRecords = [(1, "Apples", 4.59),
               (2, "Grapes", 5.99),
               (3, "Pumpkin", 3.00),
               (4, "Strawberries", 2.50),
               (5, "Leafy Greens", 4.00)]
        
cursor.executemany("INSERT OR IGNORE INTO productList (productID, productName, productPrice) VALUES(?,?,?);", productRecords)

connection.commit()

cursor.execute("SELECT * FROM productList;")

produce = cursor.fetchall()

for rows in produce:
    print(rows)

connection.close()
# create list to store productID("ID"), price("price")
#with empty list as their values
#data structure to hold user items as they make their order
groceryList = []
priceList = []

total = 0
productType = 0 

#create tuples list with products
 productsList = [(1, "Apples", 4.59),
                (2, "Grapes", 5.99),
                (3, "Pumpkin", 3.00),
                (4, "Strawberries", 2.50),
                (5, "Leafy Greens", 4.00)]

# This loop terminates when user select 2.EXIT option when asked
# in try it will ask user for an option as an integer (1 or 2) 
# if correct then proceed with an if/else statement asking for user input

# It should continue and keep adding the total price * weight - BUT THIS FUNCTION DOESN'T WORK

while True:
    while True: 
        try:
            choice = int(input("1.SELECT\n2.EXIT\nPlease select 1 or 2 (from the menu) here : ")) #use new line formatting
    except ValueError:
        print("Invalid response. Please try again.")
    
    if choice == 1:
        #have user enter productID -unique identification for each product
       
        #straight into inner-loop with validation
        while True: #create inner loop to search database
            connection = sqlite3.connect('seasonalProduce.db')  #sQ search database
            cursor = connection.cursor()
            itemID = int(input("Please enter the product ID here : "))

            #To display the updates animals to screen:
            cursor.execute("SELECT * FROM productList WHERE productID = ?;", (itemID,))

            results = cursor.fetchall() #if it's there returns single row - list with 1 tuple

            if results == []:
                print("Product ID not found.")
            else:
                #if it does exist return rows
                print(results) 
                #append to groceryList[]
                groceryList.append((results))
                #access price with indexing [2]
                priceList.append((results[2]))
                
                #print(priceList)
                #Close connection to database
                connection.close()
                break

Answer 1

您的

results

是 rows 的列表，因此

results[2]

正在尝试查找不存在的第三行。你想要的是

results[0][2]

，即第一行的第三列。