python-3.x - 如何在python3中使用SQL解析器解析任何SQL获取列名和表名

Question

我能够通过使用 sql 解析来获取列名和表名，仅用于简单的选择 SQL。

有人可以帮助如何从任何复杂的 SQL 中获取列名和表名。

Answer 1

Here is a solution for extracting column names from complex sql select statements. Python 3.9

import sqlparse

def get_query_columns(sql):
    stmt = sqlparse.parse(sql)[0]
    columns = []
    column_identifiers = []

    # get column_identifieres
    in_select = False
    for token in stmt.tokens:
        if isinstance(token, sqlparse.sql.Comment):
            continue
        if str(token).lower() == 'select':
            in_select = True
        elif in_select and token.ttype is None:
            for identifier in token.get_identifiers():
                column_identifiers.append(identifier)
            break

    # get column names
    for column_identifier in column_identifiers:
        columns.append(column_identifier.get_name())

    return columns

def test():
    sql = '''
select
   a.a,
   replace(coalesce(a.b, 'x'), 'x', 'y') as jim,
   a.bla as sally  -- some comment
from
   table_a as a
where
   c > 20
'''
    print(get_query_columns(sql))

test()
# outputs: ['a', 'jim', 'sally']

Answer 2

这是在sqlparse中打印表名的方式

1) 使用 SELECT 语句

>>> import sqlparse
>>> print([str(t) for t in parse[0].tokens if t.ttype is None][0])
'dbo.table'

（或者）

2) 使用 INSERT 语句：

def extract_tables(sql):
    """Extract the table names from an SQL statment.
    Returns a list of (schema, table, alias) tuples
    """
    parsed = sqlparse.parse(sql)
    if not parsed:
        return []

    # INSERT statements must stop looking for tables at the sign of first
    # Punctuation. eg: INSERT INTO abc (col1, col2) VALUES (1, 2)
    # abc is the table name, but if we don't stop at the first lparen, then
    # we'll identify abc, col1 and col2 as table names.
    insert_stmt = parsed[0].token_first().value.lower() == "insert"
    stream = extract_from_part(parsed[0], stop_at_punctuation=insert_stmt)
    return list(extract_table_identifiers(stream))

列名可能很棘手，因为列名可能不明确甚至派生。但是，您几乎可以从任何查询或存储过程中获取列名、序列和类型。

在遇到FROM关键字之前，将获取所有列名。

def parse_sql_columns(sql):
    columns = []
    parsed = sqlparse.parse(sql)
    stmt = parsed[0]
    for token in stmt.tokens:
        if isinstance(token, IdentifierList):
            for identifier in token.get_identifiers():
                columns.append(str(identifier))
        if isinstance(token, Identifier):
            columns.append(str(token))
        if token.ttype is Keyword:  # from
            break
    return columns