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Some things that helped me Every query response in SQL is a rectangular matrix [1]. JOINs add columns sideways. UNIONs add rows vertically[2]. [1] Which is wh
by tlarkworthy 2y ago
Some things that helped me
Every query response in SQL is a rectangular matrix [1]. JOINs add columns sideways. UNIONs add rows vertically[2].
[1] Which is why tree shaped data is awkward to query in SQL in one round-trip.
[2] From this you realize why the column names have to match to apply a UNION, and why recursion is something to do with a UNION.
- fifilura 2y agoAnd if you get stuck, since it is all about rows and columns, just sketch it out in Excel. Not using formulas in Excel but just using it as a rows/columns editor. This makes it visually clearer.