Tag Archives: SQL

Equals Is Not Always Equivalent: Power Query Joins vs. SQL Joins

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Take the following M expression:

Table.Join(A, "ID", B, "ID", JoinKind.Left)

Does it behave like the below SQL (which is how a join between two tables on column ID would typically be coded in the database world)?

FROM A
  LEFT JOIN B ON A.ID = B.ID

Perhaps surprisingly, no—at least, not when the simple, innocent null is involved.

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