Why does PostgreSQL cursor.execute() command add single quotes?

Question

Simple SQL statement:

sql = "DROP TABLE IF EXISTS %s"
cursor.execute(sql, ("user_table",))

It fails with:

psycopg2.ProgrammingError: syntax error at or near "'user_table'"
LINE 1: DROP TABLE IF EXISTS 'user_table'

The single quotes in the SQL statement are the problem. If I run this it works just fine:

cursor.execute("DROP TABLE IF EXISTS user_table")

Answer 1

您只能将参数语法用于参数，而不能用于表或列名称。

Answer 2

The AsIs adapter is useful for objects whose string representation is already valid as SQL representation

from psycopg2.extensions import AsIs

sql = "DROP TABLE IF EXISTS %s"
cursor.execute(sql, (AsIs("user_table"),))