SQL / Regex挑战/难题：如何从SQL代码中删除注释（通过使用SQL查询）？

Question

要求

• 应删除单行评论（例如 - 我的评论）。
• 应删除多行评论（例如/ *我的评论* /）。
• 字符串文字的内容（例如＆＃39;这是一个多行评论：/ *我的评论* /＆＃39;）应该被忽略。
• 应忽略标识符的内容（例如＆＃34; - 第1列 - ＆＃34;）。

文字和标识符

文字和标识符可以跨越多行

单行评论

单行注释可能是代码的最后一个元素，可能不会以换行符结束。

嵌套的多行注释

在SQL Server和PostgreSQL等数据库中，可以嵌套多行注释，例如

/* outer comment /* inner comment */ */

以下代码无效，因为只有内部注释被关闭：

/* opened outer comment /* closed inner comment */

在Teradata，Oracle，MySql和SQLite等数据库中，没有嵌套注释的概念。 以下代码无效，因为评论已使用最左边的* /。

关闭

/* comment /* is closed */ ERROR */

但这是一个有效的代码：

/* comment /* still the same comment */

Answer 1

解决方案

<强> Teradata的

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-----END RSA PRIVATE KEY-----
-----BEGIN RSA PRIVATE KEY-----
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-----END RSA PRIVATE KEY-----

<强>的Oracle

with t (txt) as 
(
select     '
            select    /* comment /* yada yada yada /* / // bla bla bla  
                        1
                                    */ t1.i
                   ,''"SRC''''"''    as "This''is''the
                                ''source"

            from      t1 /* "Comment 2" - '' */ cross join t2 -- /* comment 3 */

            where     t2.v = ''/*DST"*
                                /'' -- comment 4'
)

select    regexp_replace (txt,'(''.*?''|".*?")|/\*.*?\*/|--.*?(?=[\r\n]|$)','\1',1,0,'n')     as clean_txt

from      t
;

结果

with t (txt) as 
(
select     '
            select    /* comment /* yada yada yada /* / // bla bla bla  
                        1
                                    */ t1.i
                   ,''"SRC''''"''    as "This''is''the
                                ''source"

            from      t1 /* "Comment 2" - '' */ cross join t2 -- /* comment 3 */

            where     t2.v = ''/*DST"*
                                /'' -- comment 4'

from        dual
)

select    regexp_replace (txt,'(''.*?''|".*?")|/\*.*?\*/|--.*?(?=$|\Z)','\1',1,0,'nm')

from      t
;