尝试从数据库中提取特定值

Question

我在python中有一个sqlite3表，如下所示：

CREATE TABLE words
              (ID                    INTEGER      PRIMARY KEY      AUTOINCREMENT,
               CURRENT_WORD          TEXT     NOT NULL,
               BEFORE_WORD           TEXT     NOT NULL,
               AFTER_WORD            TEXT     NOT NULL,
               OCCURANCES            INTEGER      NOT NULL)

它返回以下数据库值：

(1, u'is', u'This', u'true', 0)
(2, u'you', u'are', u'ready', 1)

我希望能够提升价值＆＃39; OCCURANCES＆＃39;来自id 2.我尝试了以下内容，然后我计划使用正则表达式解析返回的值，但我的代码似乎没有工作：

def db_check(db, words):
    conn = sqlite3.connect(db)
    c = conn.cursor()
    frequency = 0
    print("SELECT * FROM words WHERE CURRENT_WORD = '" + words[1] + "' AND BEFORE_WORD = '" + words[0] + "' AND AFTER_WORD = '" + words[2] + "'")
    for row in c.execute("SELECT * FROM words WHERE CURRENT_WORD = '" + words[1] + "' AND BEFORE_WORD = '" + words[0] + "' AND AFTER_WORD = '" + words[2] + "'"):
        print "FOUND: "
        print row
    conn.commit()
    if frequency == 0: frequency = 1
    return frequency

知道我哪里出错了吗？我在最后一部分说我的SQL错了。有没有更好的方法来做到这一点，比如准确地拉动频率？