psycopg2 从带有占位符的元组中设置 PRIMARY KEY

Question

如何根据从元组循环的值元组在 psycopg2 中设置主键？

例如我有我的元组

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

然后我想创建 table 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

遇到那种问题，你应该先尝试构建和控制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)'

有效复制 id 列。

解决方案很简单：从 meetattrs 中删除第一个标识符：

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

或者，如果您不能确定第一个元素是主键：

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 被指定了两次。

您可以以更简洁的方式构建查询：

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)'

确保你的元组的第一项总是 id

psycopg2 从带有占位符的元组中设置 PRIMARY KEY

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psycopg2