How does Hyper-Q implement complex UPDATE statements on SQL DW?

UPDATE statements on Microsoft SQL Data Warehouse are limited to simple FROM clauses, requiring a combination of CTAS and an implicit join to implement complex source expressions for an UPDATE Please see Section "AH. ANSI join replacement for update statements" in https://docs.microsoft.com/en-us/sql/t-sql/queries/update-transact-sql?view=azure-sqldw-latest#ah-ansi-join-replacement-for-update-statements for details.

Datometry Hyper-Q transparently allows existing applications to run complex UPDATE statements against SQL DW by automatically breaking the client request into CTAS and UPDATE as recommended in the article referenced above. In addition, Hyper-Q's emulation for UPDATEs also ensures that Teradata semantics are maintained, including multiple source rows updating a single target row.

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