如何从 SQL 查询中的 CREATE/UPDATE/INSERT 语句中提取表名？

Question

我正在尝试解析存储在表列中的以下 sql 查询创建、插入或更新的表。

我们将表格列称为query。以下是一些示例数据，用于展示数据的外观变化。

with sample_data as (
  select 1 as id, 'CREATE TABLE tbl1 ...' as query union all
  select 2 as id, 'CREATE OR REPLACE TABLE tbl1 ...' as query union all
  select 3 as id, 'DROP TABLE IF EXISTS tbl1; CREATE TABLE tbl1 ...' as query union all
  select 4 as id, 'INSERT /*some comment*/ INTO tbl2 ...' as query union all
  select 5 as id, 'INSERT /*some comment*/ INTO tbl2 ...' as query union all
  select 6 as id, 'UPDATE tbl3 SET col1 = ...' as query union all
  select 7 as id, '/*some garbage comments*/ UPDATE tbl3 SET col1 = ...' as query union all  
  select 8 as id, 'DELETE tbl4 ...' as query
),

以下是查询的格式（我们正在尝试提取 table_name）：

#1 some optional statements like drop table 创建some comments or optional statement like OR REPLACE 表table_name everything else

#2 some optional statements like drop table 插入some comments 插入some comments table_name

#3 some optional statements like drop table 更新some comments table_name everything else

Answer 1

正则表达式

要构造一个合适的正则表达式，让我们从以下相对简单/可读的版本开始：

((CREATE( OR REPLACE)?|DROP) TABLE( IF EXISTS)?|UPDATE|DELETE|INSERT INTO) ([^\s\/*]+)

以上所有空格都可以替换为“至少一个空格字符”，即\s+。但是我们还需要允许 cmets。对于看起来像/*anything*/ 的评论，正则表达式看起来像\/\*.*\*\/ （其中评论字符用\ 转义，“anything”是中间的.*）。鉴于可能有多个这样的 cmets，可选用空格分隔，我们最终得到 (\s*\/\*.*\*\/\s*?)*\s+。将其插入任何有空间的地方：

((CREATE((\s*\/\*.*\*\/\s*?)*\s+OR(\s*\/\*.*\*\/\s*?)*\s+REPLACE)?|DROP)(\s*\/\*.*\*\/\s*?)*\s+TABLE((\s*\/\*.*\*\/\s*?)*\s+IF(\s*\/\*.*\*\/\s*?)*\s+EXISTS)?|UPDATE|DELETE|INSERT(\s*\/\*.*\*\/\s*?)*\s+INTO)(\s*\/\*.*\*\/\s*?)*\s+([^\s\/*]+)

需要进一步改进：括号中的表达式已用于选择，例如(CHOICE1|CHOICE2)。但是这种语法将它们包括为捕获组。实际上，我们只需要一个捕获组作为表名，因此我们可以通过?: 排除所有其他捕获组，例如(?:CHOICE1|CHOICE2)。这给出了：

(?:(?:CREATE(?:(?:\s*\/\*.*\*\/\s*?)*\s+OR(?:\s*\/\*.*\*\/\s*?)*\s+REPLACE)?|DROP)(?:\s*\/\*.*\*\/\s*?)*\s+TABLE(?:(?:\s*\/\*.*\*\/\s*?)*\s+IF(?:\s*\/\*.*\*\/\s*?)*\s+EXISTS)?|UPDATE|DELETE|INSERT(?:\s*\/\*.*\*\/\s*?)*\s+INTO)(?:\s*\/\*.*\*\/\s*?)*\s+([^\s\/*]+)

在线正则表达式演示

这是一个与您的示例一起使用的演示：Regex101 demo

SQL

REGEXP_EXTRACT 的 Google BigQuery 文档说它将返回与捕获组匹配的子字符串。所以我希望这样的事情能够奏效：

with sample_data as (
  select 1 as id, 'CREATE TABLE tbl1 ...' as query union all
  select 2 as id, 'CREATE OR REPLACE TABLE tbl1 ...' as query union all
  select 3 as id, 'DROP TABLE IF EXISTS tbl1; CREATE TABLE tbl1 ...' as query union all
  select 4 as id, 'INSERT /*some comment*/ INTO tbl2 ...' as query union all
  select 5 as id, 'INSERT /*some comment*/ INTO tbl2 ...' as query union all
  select 6 as id, 'UPDATE tbl3 SET col1 = ...' as query union all
  select 7 as id, '/*some garbage comments*/ UPDATE tbl3 SET col1 = ...' as query union all  
  select 8 as id, 'DELETE tbl4 ...' as query
)

SELECT
  *, REGEXP_EXTRACT(query, r"(?:(?:CREATE(?:(?:\s*\/\*.*\*\/\s*?)*\s+OR(?:\s*\/\*.*\*\/\s*?)*\s+REPLACE)?|DROP)(?:\s*\/\*.*\*\/\s*?)*\s+TABLE(?:(?:\s*\/\*.*\*\/\s*?)*\s+IF(?:\s*\/\*.*\*\/\s*?)*\s+EXISTS)?|UPDATE|DELETE|INSERT(?:\s*\/\*.*\*\/\s*?)*\s+INTO)(?:\s*\/\*.*\*\/\s*?)*\s+([^\s\/*]+)") AS table_name
FROM sample_data;

（以上内容未经测试，如有任何问题，请在 cmets 中告诉我。）

Answer 2

我认为这确实取决于您的数据，但使用这样的方法您可能会发现一些成功：

with data as (
  select 1 as id, 'CREATE TABLE tbl1 ...' as query union all
  select 2 as id, 'INSERT INTO tbl2 ...' as query union all
  select 3 as id, 'UPDATE tbl3 ...' as query union all
  select 4 as id, 'DELETE tbl4 ...' as query
),
splitted as (
  select id, split(query, ' ') as query_parts from data
)
select
  id,
  case 
    when query_parts[safe_offset(0)] in('CREATE', 'INSERT') then query_parts[safe_offset(2)]
    when query_parts[safe_offset(0)] in('UPDATE', 'DELETE') then query_parts[safe_offset(1)]
    else 'Error'
  end as table_name
from splitted

当然，这取决于您的query 列中的清洁度和语法。此外，如果您的 table_name 符合 project.table.dataset 条件，则需要进一步拆分。