Self-Join vs LAG for Adjacent Rows

Concepts covered: sqlRecursiveCte

The escalation at this level is depth. A self-join handles one level of hierarchy. Two self-joins handle two levels. Three handle three. At some depth, the chained-join approach breaks down: either because the hierarchy is unbounded, or because the code becomes unreadable, or because the engine's join planner gives up. The pivot point is when you switch to a recursive CTE. Knowing where that pivot point is , and being able to defend the choice , is the depth signal at this level. The chained-self-join approach Each level adds one LEFT JOIN. The query reads top-down: employee, their manager, their manager's manager, and so on. LEFT JOIN handles missing levels (the CEO has no manager). The pattern works cleanly up to about four levels; beyond that the query becomes unreadable and the join pl

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