Hi, @AndyR123
Query folding may occur for an entire Power Query query, or for a subset of its steps. When query folding cannot be achieved—either partially or fully—the Power Query mashup engine must compensate by processing data transformations itself.
Generally, the following list describes transformations that can be query folded.
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Removing columns.
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Renaming columns (SELECT column aliases).
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Filtering rows, with static values or Power Query parameters (WHERE clause predicates).
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Grouping and summarizing (GROUP BY clause).
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Expanding record columns (source foreign key columns) to achieve a join of two source tables (JOIN clause).
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Non-fuzzy merging of fold-able queries based on the same source (JOIN clause).
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Appending fold-able queries based on the same source (UNION ALL operator).
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Adding custom columns with simple logic (SELECT column expressions). Simple logic implies uncomplicated operations, possibly including the use of M functions that have equivalent functions in the SQL data source, like mathematic or text manipulation functions.
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Pivoting and unpivoting (PIVOT and UNPIVOT operators).
Best Regards,
Community Support Team _Charlotte
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