SQL 连接子句中的 table1.{0} == table2.{0} 是什么意思？

Question

我正在尝试理解以下代码片段：

    improt pandasql

    data_sql = data[['account_id', 'id', 'date', 'amount']]
    # data_sql is a table has the above columns

    data_sql.loc[:, 'date_hist_min'] = data_sql.date.apply(lambda x: x + pd.DateOffset(months=-6))
    # add one more column, 'date_hist_min', it is from the column 'data' with the month minus 6

    sqlcode = '''
    SELECT  t1.id,
            t1.date,
            t2.account_id as "account_id_hist",
            t2.date as "date_hist",
            t2.amount as "amount_hist"

        FROM data_sql as t1 JOIN data_sql as t2
            ON (cast(strftime('%s', t2.date) as integer) BETWEEN
                (cast(strftime('%s', t1.date_hist_min) as integer))
                AND (cast(strftime('%s', t1.date) as integer)))
            AND (t1.{0} == t2.{0})
    '''
    # perform the SQL query on the table with sqlcode:
    newdf = pandasql.sqldf(sqlcode.format(column), locals())

代码与Python pandasql。它将数据帧操作为 SQL table。你可以假设上面的数据框为 SQL table。

table的定义在评论里。

t1.{0} == t2.{0} 是什么意思？ {0} 在上下文中代表什么？

Answer 1

sqlcode.format(column) 正在格式化字符串并将列注入 {0}

0表示格式将使用第一个参数。

print("This {1} a {0}".format("string", "is")) 会打印 "This is a string"

SQL 连接子句中的 table1.{0} == table2.{0} 是什么意思？

What's the meaning of table1.{0} == table2.{0} in SQL join clause?

python

sql

pandasql