[GitHub] [spark] peter-toth commented on pull request #34693: [SPARK-37259][SQL] Support CTE and TempTable queries with MSSQL JDBC

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peter-toth commented on pull request #34693:
URL: https://github.com/apache/spark/pull/34693#issuecomment-984501867


   > > Unfortunately, it is non-trivial to split an arbitrary query it into "with" and "regular" clauses in MsSqlServerDialect.
   > 
   > Could you please show us some example queries where the split is non-trivial?
   
   For example:
   ```
     WITH t AS (SELECT x FROM tbl), t2 AS (SELECT y FROM tbl2) SELECT * FROM t WHERE x > SELECT max(y) FROM t2 
   ```
   You need to split this to `WITH t AS (SELECT x FROM tbl), t2 AS (SELECT y FROM tbl2)` and `SELECT * FROM t WHERE x > SELECT max(y) FROM t2`. Obviously there can be more brackets in the query and some might not be paired/closed if they appear in strings like: `t2 AS (SELECT y, ')' AS dummy FROM tbl2)`. We could use ANTLR to parse the query just like we use it to parse Spark SQL statements but I'm not sure it is worth it...


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