Python & SQLite3 从两个表中选择

Question

我已经用Python编写了这段代码，我基本上打开了我的SQLite3数据库并查看表“联系人”中的每一行，然后获取每个“id”号码，然后查看表“用户”中匹配的“id” 。我的问题是它只输出第一个，而不循环所有行。

import sqlite3

conn = sqlite3.connect('sqlite3.db')

cursor = conn.cursor()
cursor2 = conn.cursor()
cursor3 = conn.cursor()

text_file = open("Output.txt", "w");
try:
    cursor.execute("SELECT Id, address FROM contact;") # Get address details by ID
    for row in cursor:
        ID = row[0]
        address= row[1]

        cursor2.execute("SELECT name FROM Users WHERE id= " + str(ID) + ";") # Get users's name by ID
        row2 = cursor2.fetchone()
        sendername = row2[0]

        text_file.write(firstname, lastname, address);


finally:
    conn.close()

任何建议，我对 python 很陌生。

Answer 1

您可以要求数据库进行连接：

cursor.execute("""\
    SELECT u.name, c.address
    FROM contact c
    INNER JOIN Users u ON u.id = c.Id
    """)
with open('Output.txt', 'w') as outfh:
    for name, address in cursor:
        outfh.write('{} {}\n'.format(name, address)

告诉INNER JOINSQLite 仅选择列上存在实际匹配的行id。如果您将该id列标记为表中的外键contact，则也可以使用 aNATURAL INNER JOIN并省略该ON子句。