python - 使用 Python 检查 PostgreSQL 表中是否存在列

Question

我搜索了很长时间的答案并做了以下事情:

(1)

query = "SELECT COUNT(*) FROM %s WHERE user_name = %s" % (table_name, username)
result = conn.query(query).result()[0][0]
if result == 0:
    (do something)

(2)

query = "SELECT 1 FROM %s WHERE user_name = %s" %(table_name, username)
result = conn.query(query).result()[0][0]
if result == ' ':
    (do something)

(3)

query = "SELECT EXISTS (SELECT 1 FROM %s WHERE user_name = %s)" %(table_name, username)
result = conn.query(query).result()[0][0]
if result == 't':
    (do something)

但都不起作用...错误始终是:

column "Tom" does not exist

因为它真的不存在，我只想检查它是否存在。感谢您的帮助。

Answer 1

sql = """SELECT count(*)
         FROM information_schema.columns
         WHERE table_name = '%s'
         AND column_name = '%s'
      """ % (thetable,thecolumn)