psycopg2.ProgrammingError：列不存在

Question

当我尝试通过 python.roll_no 对数据库进行查询时，我收到以下错误，这是表中的关键。

File "class_room.py", line 30, in get
cursor.execute("select first_name from class_room where keyword=%s",     (roll_no))
psycopg2.ProgrammingError: column "keyword" does not exist
LINE 1: select first_name from class_room where keyword='3'


                                           ^
12:21 class_room=# \d+ class_room
                               Table "public.class_room"
  Column   |  Type   |         Modifiers         | Storage  | Stats target |   Description
------------+---------+---------------------------+----------+--------------+-      ------------
roll_no    | integer | not null                  | plain    |              |
first_name | text    | not null default ''::text | extended |              |
last_name  | text    | not null default ''::text | extended |              |
marks      | integer |                           | plain    |              |
Indexes:
   "class_room_pkey" PRIMARY KEY, btree (roll_no)
Has OIDs: no



user:~/pathclass_room $ cat schema.sql
create table class_room (
roll_no int primary key,
first_name text not null default '',
last_name text not null default '',
marks int
);

Answer 1

改为：

cursor.execute("select first_name from class_room where roll_no = %s", (roll_no,))

roll_no 后不要省略逗号。它将带括号的表达式变成一个元组。