SQL Connector for HiveQL

The native query language supported by Spark is HiveQL. For simple queries, HiveQL is a subset of SQL-92. However, the syntax is different enough that most applications do not work with native HiveQL.

To bridge the difference between SQL and HiveQL, the SQL Connector feature translates standard SQL-92 queries into equivalent HiveQL queries. The SQL Connector performs syntactical translations and structural transformations. For example:

• Quoted Identifiers: The double quotes (") that SQL uses to quote identifiers are translated into back quotes (`) to match HiveQL syntax. The SQL Connector needs to handle this translation because even when a connector reports the back quote as the quote character, some applications still generate double-quoted identifiers.
• Table Aliases: Support is provided for the AS keyword between a table reference and its alias, which HiveQL normally does not support.
• JOIN, INNER JOIN, and CROSS JOIN: SQL JOIN, INNER JOIN, and CROSS JOIN syntax is translated to HiveQL JOIN syntax.
• TOP N/LIMIT: SQL TOP N queries are transformed to HiveQL LIMIT queries.

Related topics

• spark_system Table
• Get Tables With Query
• Data Types
• Write-back
• Features