如何在我的情况下使用Executemany？

Question

我该如何让这些SQL语句顺利运行呢？之前我只处理过单个的select语句，使用cursor.execute的时候一切都很顺利。但现在我不知道该怎么做。现在我遇到的错误是format requires a mapping。

args =  {
        "timepattern" : timepattern,
        "datestart_int" : datestart_int,
        "dateend_int" : dateend_int
        }
sql = ( "CREATE TEMPORARY TABLE cohort_users (user_id INTEGER);                                "
            "INSERT INTO cohort_users (user_id)                                                    "
            "SELECT id FROM users WHERE registered_at BETWEEN %(datestart_int)s AND %(dateend_int)s;                        "
            "SELECT 1, FROM_UNIXTIME(%(dateend_int)s, %(timepattern)s)                                                    "
            "UNION ALL                                                                            "
            "SELECT (COUNT(DISTINCT x.user_id)/(SELECT COUNT(1) FROM cohort_users)),             "
            "        FROM_UNIXTIME((%(dateend_int)s + (7 * 24 * 60 * 60)), %(timepattern)s)                                "
            "FROM cohort_users z INNER JOIN actions x ON x.user_id = z.id                        "
            "WHERE x.did_at BETWEEN (%(datestart_int)s + (7 * 24 * 60 * 60)) AND (%(dateend_int)s + (7 * 24 * 60 * 60))        "
            "DROP TABLE cohort_users;                                                            "
            )

cursor.executemany(sql,args)

Answer 1

executemany() 是用来对多个参数执行同一个语句的。

而你想要的是反过来：对每个语句单独调用 execute()。

Answer 2

假设你的数据库软件支持用 %(name)s 这种形式的占位符。

还假设它支持在一个“操作”中执行多个语句。注意：第三个语句（SELECT ... UNION ALL SELECT ...）最后缺少一个分号。

在这种情况下，你只需要使用 cursor.execute(sql, args) ... executemany() 是用来处理一系列参数的（比如用来执行多个插入操作）。

为了方便移植和调试，最好是一次执行一个语句。

使用三重引号（并且用结构化的缩进，而不是宽缩进）会让你的 SQL 更容易阅读：

sql = """
CREATE TEMPORARY TABLE cohort_users (user_id INTEGER);   

INSERT INTO cohort_users (user_id)
    SELECT id
        FROM users
        WHERE registered_at BETWEEN %(datestart_int)s AND %(dateend_int)s
    ;

SELECT  1, FROM_UNIXTIME(%(dateend_int)s, %(timepattern)s)
UNION ALL
SELECT  (COUNT(DISTINCT x.user_id)/(SELECT COUNT(1) FROM cohort_users)), 
        FROM_UNIXTIME((%(dateend_int)s + (7 * 24 * 60 * 60)), (timepattern)s)
    FROM cohort_users z
    INNER JOIN actions x ON x.user_id = z.id
    WHERE x.did_at BETWEEN (%(datestart_int)s + (7 * 24 * 60 * 60))
    AND (%(dateend_int)s + (7 * 24 * 60 * 60))
    ;

DROP TABLE cohort_users;
"""