使用 python 在多个字符串中查找并计算 substring 的实例

Question

我在 python 中有一个带有多个子查询的 sql 查询。 所以设置是一个较大字符串中的多个子字符串。 我想检查子字符串中字符串的实例数。 比我所看到的更多参与并感谢您的帮助。

像这样设置 -

qry = ''' 
with 
qry_1 as ( 
   SELECT ID, 
          NAME
   FROM   ( ... other code...
),
qry_2 as ( 
    SELECT coalesce (table1.ID, table2.ID) as ID,
           NAME
   FROM (...other code...
),
qry_3 as (
     SELECT id.WEATHER AS WEATHER_MORN,
            ROW_NUMBER() OVER(PARTITION BY id.SUN
                ORDER BY id.TIME) AS SUN_TIME,
            id.RAIN,
            id.MIST
   FROM (...other code..
)
'''

我想计算qry_1, qry_2, qry_3内的ID实例。

我认为会利用re.findall和 substring 搜索？

re.findall(r'as \( select (.+?) from \(',qry)

然后在其中查找和计算ID实例？ output 是 2。但我不确定如何......

Answer 1

您可以拆分 CTE 查询，然后在子查询的截断版本上使用re.findall ：

qry = ''' 
with 
qry_1 as ( 
  SELECT ID, 
      NAME
  FROM   ( ... other code...
),
qry_2 as ( 
  SELECT coalesce (table1.ID, table2.ID) as ID,
       NAME
FROM (...other code...
),
qry_3 as (
  SELECT WEATHER
FROM (...other code..
)
'''

def get_cols(s):
   [cte_name] = re.findall('^\w+(?=\sas)|(?<=with\s)\w+(?=\sas)', s)
   cols = re.findall('(?<=as\s)[\w\.]+|(?<=SELECT\s)[\w\.]+|(?<=,\s)[\w\.]+', s)
   return [cte_name, cols]

#dictionary with the cte name as the key, and the columns as the values
v = dict(get_cols(re.sub('coalesce\s\(.+\)|[\s\n]+', ' ', i)) for i in re.split('(?<=\)),(?:\s+)*\n', qry))
#filter the dictionary above to only include desired column names
r = {a:k if (k:=[i for i in b if i in {'NAME', 'ID'}]) else None for a, b in v.items()}

Output：

{'qry_1': ['ID', 'NAME'], 'qry_2': ['ID', 'NAME'], 'qry_3': None}