Python SQLite如何使用'？'进行部分搜索？ 占位符？

Question

假设我的查询如下所示：

q = SELECT * FROM MY_TABLE WHERE FIELD LIKE ?
cursor.execute(q, some_query_value)

这似乎没有进行“包含”搜索，所以我尝试这样做

q = SELECT * FROM MY_TABLE WHERE FIELD LIKE %?%
cursor.execute(q, some_query_value)

但是python似乎不喜欢这个。 这样做的正确方法是什么？

Answer 1

%通配符是要插值的值的一部分; 使用字符串连接或格式将其添加到要搜索的值中，而不是在查询中：

q = "SELECT * FROM MY_TABLE WHERE FIELD LIKE ?"
cursor.execute(q, ('%' + some_query_value + '%',))

要么

q = "SELECT * FROM MY_TABLE WHERE FIELD LIKE ?"
cursor.execute(q, ('%{}%'.format(some_query_value),))

现在， sqlite3可以正确引用value-with-wildcards进行插值。

Answer 2

尝试在查询字符串周围添加引号并在查询值中放置通配符：

q = '''SELECT * FROM MY_TABLE WHERE FIELD LIKE ?'''
some_query_value = '%test%'
cursor.execute(q, [some_query_value])

Answer 3

这是一个独立的示例，演示如何使用通配符进行查询。

import sqlite3

conn = sqlite3.connect(':memory:')
c = conn.cursor()
c.execute('create table methodists (name text)')

c.executemany("insert into methodists VALUES (?)",
              [['George Lucas'], ['George W. Bush'], ['W. C. Handy']])

c.execute('select name from  methodists where name like ?', ['George%'])
print ', '.join(name for name, in c.fetchall())

c.execute('select name from methodists where name like ?', ['%W.%'])
print ', '.join(name for name, in c.fetchall())

结果：

George Lucas, George W. Bush
George W. Bush, W. C. Handy