liancheng commented on a change in pull request #24809: [SPARK-21136][SQL]
Disallow FROM-only statements and show better warnings for Hive-style
single-from statements
URL: https://github.com/apache/spark/pull/24809#discussion_r292659773
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File path: docs/sql-migration-guide-upgrade.md
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@@ -23,6 +23,7 @@ license: |
{:toc}
## Upgrading From Spark SQL 2.4 to 3.0
+ - In Spark version 2.4 and earlier, SQL queries such as `FROM test` or `FROM
test UNION ALL FROM test` are supported by accident. In hive-style `FROM test
SELECT *`, the `SELECT` clause is not negligible. Therefore we will treat these
queries as invalid since Spark 3.0.
Review comment:
@yeshengm BTW, we should also mention that neither Hive nor Presto ever
supported the syntax `FROM <table-name>`. That's part of the reason why we
considered it as "supported by accident".
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