sqlite3.OperationalError - 试图停止重复结果答案

【问题标题】：sqlite3.OperationalError - Trying to stop duplication of resultssqlite3.OperationalError - 试图停止重复结果
【发布时间】：2017-08-02 20:42:36
【问题描述】：

我希望这段代码创建一个表并且每次只打印一个列表，而不是打印多个（之前运行时的结果）。我如何修复此代码以使 WHERE NOT EXISTS 代码真正起作用。

我的错误是：

Traceback (most recent call last):
line 33, in <module>
data_entry()
line 14, in data_entry
c.execute("INSERT INTO myTestTable VALUES('James', 45, 'Home') WHERE NOT EXISTS (SELECT 1 FROM myTestTable WHERE name ='james' AND age =45 AND address ='school')") 
sqlite3.OperationalError: near "WHERE": syntax error

代码：

import sqlite3 

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

c = conn.cursor() 

param = "School" 


def create_table():
    c.execute('CREATE TABLE IF NOT EXISTS myTestTable(name TEXT, age REAL, address TEXT)') 

def data_entry():
    c.execute("INSERT INTO myTestTable VALUES('James', 45, 'Home') WHERE NOT EXISTS (SELECT 1 FROM myTestTable WHERE name ='james' AND age =45 AND address ='school')")
    c.execute("INSERT INTO myTestTable VALUES('Jeff', 16, 'School') WHERE NOT EXISTS (SELECT 1 FROM myTestTable WHERE name ='james' AND age =45 AND address ='school')")
    c.execute("INSERT INTO myTestTable VALUES('Bob', 14, 'School') WHERE NOT EXISTS (SELECT 1 FROM myTestTable WHERE name ='james' AND age =45 AND address ='school')")
    c.execute("INSERT INTO myTestTable VALUES('Jack', 15, 'School') WHERE NOT EXISTS (SELECT 1 FROM myTestTable WHERE name ='james' AND age =45 AND address ='school')")
    conn.commit()

def query1():
    c.execute("SELECT * FROM myTestTable WHERE address = ?",(param,)) 
    while True:
        row=c.fetchone()
        if row == None:
            break
        print(row)

    c.close()
    conn.close()

create_table()

data_entry()

query1()

【问题讨论】：

顺便说一句，我认为您之前的问题（及其答案）在这里让您走错了路。您仅对 james 条目进行了硬编码，因此如果您的语法正常工作，它不会阻止您复制其他条目。超出您的 3 个测试条目，这种方法将变得站不住脚。

标签： python sql python-3.x sqlite

【解决方案1】：

sqlite 不支持插入语句中的where 子句。我相信您想要做的是将unique 约束添加到表并使用insert or ignore。

c.execute('CREATE TABLE IF NOT EXISTS myTestTable(name TEXT, age REAL, address TEXT, UNIQUE(name, age, address))') 

c.execute("INSERT OR IGNORE INTO myTestTable VALUES('James', 45, 'Home')")

详情见下文：

这也是一个可扩展的解决方案，避免了@raganjosh 指出的问题。但是，您可能希望以通知用户的方式处理重复。

【讨论】：