在函数名上拆分SQL语句，但在Python中保留分隔符

Question

假设我有下面的string，其中包含从SELECT子句中提取的SQL语句（实际上，这是一个包含数百个这样的语句的巨大SQL语句）

  SUM(case when(A.money-B.money>1000
                and A.unixtime-B.unixtime<=890769
                and B.col10 = "A"
                and B.col11 = "12"
                and B.col12 = "V") then 10
      end) as finalCond0,
  MAX(case when(A.money-B.money<0
                and A.unixtime-B.unixtime<=6786000
                and B.cond1 = "A"
                and B.cond2 = "4321"
                and B.cond3 in ("E", "F", "G")) then A.col10
        end) as finalCond1,
  SUM(case when(A.money-B.money>0
                and A.unixtime-B.unixtime<=6786000
                and B.cond1 = "A"
                and B.cond2 = "1234"
                and B.cond3 in ("A", "B", "C")) then 2
      end) as finalCond2    

如何在函数（即SUM、MAX、MIN、MEAN等）上拆分此查询，以便在不删除分隔符的情况下提取最后一个查询（在本例中是SUM）？在

因此，所需的输出将是一个如下所示的字符串：

^{pr2}$

PS：出于表示目的，我提供了一些缩进，但实际上这些语句是用逗号分隔的，这意味着原始格式中没有空白或新行。在

Answer 1

在这里不能使用正则表达式，因为SQL语法不形成可以与Pythonre引擎匹配的正则模式。实际上，您必须将字符串解析为令牌流或语法树；毕竟，SUM(...)可以包含大量语法，包括子选择。在

^{} library可以这样做，即使它是bit underdocumented and not that friendly to external uses。在

重新使用我在链接到的另一篇文章中定义的walk_tokens函数：

from collections import deque
from sqlparse.sql import TokenList

def walk_tokens(token):
    queue = deque([token])
    while queue:
        token = queue.popleft()
        if isinstance(token, TokenList):
            queue.extend(token)
        yield token

从SELECT标识符列表中提取最后一个元素是：

^{pr2}$

演示：

>>> sql = '''\
...   SUM(case when(A.money-B.money>1000
...                 and A.unixtime-B.unixtime<=890769
...                 and B.col10 = "A"
...                 and B.col11 = "12"
...                 and B.col12 = "V") then 10
...       end) as finalCond0,
...   MAX(case when(A.money-B.money<0
...                 and A.unixtime-B.unixtime<=6786000
...                 and B.cond1 = "A"
...                 and B.cond2 = "4321"
...                 and B.cond3 in ("E", "F", "G")) then A.col10
...         end) as finalCond1,
...   SUM(case when(A.money-B.money>0
...                 and A.unixtime-B.unixtime<=6786000
...                 and B.cond1 = "A"
...                 and B.cond2 = "1234"
...                 and B.cond3 in ("A", "B", "C")) then 2
...       end) as finalCond2
... '''
>>> tokens = sqlparse.parse(sql)[0]
>>> for tok in walk_tokens(tokens):
...     if isinstance(tok, IdentifierList):
...         # iterate to leave the last assigned to `identifier`
...         for identifier in tok.get_identifiers():
...             pass
...         break
...
>>> print(identifier)
SUM(case when(A.money-B.money>0
                and A.unixtime-B.unixtime<=6786000
                and B.cond1 = "A"
                and B.cond2 = "1234"
                and B.cond3 in ("A", "B", "C")) then 2
      end) as finalCond2

identifier是一个sqlparse.sql.Identifier实例，但是再次将其转换为字符串（这是print()所做的，或者您可以只使用str()）为该部分再次提供输入SQL字符串。在