Question

如何从元组中循环的元组中设置psycopg2中的主键？

例如我有我的元组

meetattrs = ('id', 'venue', 'date', 'rail', 'weather', 'trackcondition')

然后我想创建表并提取和插入值。从meetattrs我希望将id设置为主键。

conn = psycopg2.connect("")
with conn, conn.cursor() as cur:
        # First, create tables.
    cur.execute("drop table if exists meetings, races, horses")
    cur.execute("create table meetings (id integer PRIMARY KEY, " +
                ", ".join("%s varchar" % fld for fld in meetattrs)
                + ")")

然而，这会产生此错误，不确定如何解决。

Traceback (most recent call last):
  File "racemeeting.py", line 56, in <module>
    + ")")
psycopg2.ProgrammingError: column "id" specified more than once

Answer 1

在这种问题中，您应该首先尝试构建和控制sql字符串。

("create table meetings (id integer PRIMARY KEY, " +
            ", ".join("%s varchar" % fld for fld in meetattrs)
            + ")")

给出：

'create table meetings (id integer PRIMARY KEY, id varchar, venue varchar, date varchar, rail varchar, weather varchar, trackconditionvarchar)'

有效地复制id列。

解决方案很简单：从meetattrs删除第一个标识符：

cur.execute("create table meetings (id integer PRIMARY KEY, " +
            ", ".join("%s varchar" % fld for fld in meetattrs[1:])
            + ")")

或者，如果你不能确定主键是否为第一个元素：

cur.execute("create table meetings (id integer PRIMARY KEY, " +
            ", ".join("%s varchar" % fld for fld in meetattrs if fld != 'id')
            + ")")

Answer 2

在执行join并且占位符获取其值后，您当前的SQL查询是：

'create table meetings (id integer PRIMARY KEY, id varchar, venue varchar, date varchar, rail varchar, weather varchar, trackcondition varchar)'

id指定了两次。

您可以更清晰地构建查询：

query_params = " %s integer PRIMARY KEY" + ", %s varchar" * (len(meetattrs) - 1)

您的SQL语句变为：

"create table meetings (" + query_params % meetattrs + ")"

插入占位符值后：

'create table meetings (id integer PRIMARY KEY, venue varchar, date varchar, rail varchar, weather varchar, trackcondition varchar)'

确保您的元组的第一项始终为id

psycopg2使用占位符从元组设置PRIMARY KEY

2 个答案: