我真的不认为正则表达式是安全的方法。要处理的事情真的太多了，比如评论，工会等等
我用SQLGlot库玩了一把，代码如下：

##python3 -m pip install sqlglot

from sqlglot import parse_one, exp

queries = [
"""
INSERT INTO a.test
(
test1,
test2
)
select 
test1,
test2
from 
xyz.test
""",
"""
/*******************************************************                                                                                
    MACRO                                                                 
        abc.test
    PURPOSE                                   
         TO DELETE THE DATA FROM abc.test
    INPUT PARAMS                              
                   NONE                                                                      
    CALLED BY                                                                            
        THIS MACRO IS BEING CALLED FROM sql
*******************************************************/ 
    DELETE FROM sample.test
""",
"""
SELECT
  t1.firstname,
  t1.lastname,
  t2.email,
  t3.order
FROM abc.table1 t1
LEFT JOIN abc.table2 t2 ON t2.id = t1.id
LEFT JOIN abc.table3 t3 ON t3.email = t2.email
""",
"""
SELECT id, name FROM table1
UNION
SELECT id, name FROM table2
"""
]

for query in queries:
    print(query)
    sourceTables = []
    for select in parse_one(query).find_all(exp.Select):
        for table in select.find_all(exp.Table):
            sourceTables.append(str(table))
    print("Source tables:")
    print(sourceTables)
    print("\n")

它输出以下内容：

INSERT INTO a.test
(
test1,
test2
)
select 
test1,
test2
from 
xyz.test

Source tables:
['xyz.test']


/*******************************************************                                                        

    MACRO
        abc.test
    PURPOSE
         TO DELETE THE DATA FROM abc.test
    INPUT PARAMS
                   NONE
    CALLED BY
        THIS MACRO IS BEING CALLED FROM sql
*******************************************************/
    DELETE FROM sample.test

Source tables:
[]


SELECT
  t1.firstname,
  t1.lastname,
  t2.email,
  t3.order
FROM abc.table1 t1
LEFT JOIN abc.table2 t2 ON t2.id = t1.id
LEFT JOIN abc.table3 t3 ON t3.email = t2.email

Source tables:
['abc.table1 AS t1', 'abc.table2 AS t2', 'abc.table3 AS t3']


SELECT id, name FROM table1
UNION
SELECT id, name FROM table2

Source tables:
['table1', 'table2']

似乎如你所愿...

下面将从提供的两个示例中获取值。
需要注意的是，“delete”、“from” 或 “join” 是该行上的第一个非空白字符序列。

(?is)^\s*(?:delete\s+)?(?:from|join)\s*.*?([^\s]+)

• （？is）* 将切换到 * 忽略大小写 * 和 * 单行 * 模式。

输出量

xyz.test
sample.test