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https://issues.apache.org/jira/browse/SPARK-20964?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16408578#comment-16408578
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Frederick Reiss commented on SPARK-20964:
-----------------------------------------
SQL2016 prohibits the use of reserved words in unquoted identifiers. See
[http://jtc1sc32.org/doc/N2301-2350/32N2311T-text_for_ballot-CD_9075-2.pdf],
page 176:
_26) The case-normal form of <regular identifer> shall not be equal, according
to the comparison rules in Subclause 8.2, “<comparison predicate>”, to any
<reserved word> (with every letter that is a lower-case letter replaced by the
corresponding upper-case letter or letters), treated as the repetition of a
<character string literal> that specifes a <character set specifcation> of
SQL_IDENTIFIER._
That said, strict enforcement of that rule will break existing queries every
time a new reserved word is added. This factor in turn leads users to start
quoting *every* identifier as a defensive measure. You end up with SQL like
this:
{{SELECT "R"."A", "S"."B"}}
{{ FROM "MYSCHEMA"."R" as "R", "MYSCHEMA"."S" as "S"}}
DB2 allows reserved words to be used unquoted; for example, {{SELECT * FROM
SYSIBM.SYSTABLES WHERE, WHERE}} (see
[https://www.ibm.com/support/knowledgecenter/en/SSEPEK_11.0.0/sqlref/src/tpc/db2z_reservedwords.html]),
which lets users use a more literate form of SQL.
> Make some keywords reserved along with the ANSI/SQL standard
> ------------------------------------------------------------
>
> Key: SPARK-20964
> URL: https://issues.apache.org/jira/browse/SPARK-20964
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 2.1.1
> Reporter: Takeshi Yamamuro
> Priority: Minor
>
> The current Spark has many non-reserved words that are essentially reserved
> in the ANSI/SQL standard
> (http://developer.mimer.se/validator/sql-reserved-words.tml).
> https://github.com/apache/spark/blob/master/sql/catalyst/src/main/antlr4/org/apache/spark/sql/catalyst/parser/SqlBase.g4#L709
> This is because there are many datasources (for instance twitter4j) that
> unfortunately use reserved keywords for column names (See [~hvanhovell]'s
> comments: https://github.com/apache/spark/pull/18079#discussion_r118842186).
> We might fix this issue in future major releases.
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