CTE Query Performance
The following question came up when working on my CTE presentation for SQL Saturday. Does a query that JOINs a CTE to itself execute the CTE query once or twice? For instance: ;WITH deptCTE(id, department, parent) AS (SELECT id,department,parent FROM Departments)SELECT q1.department,q2.department FROM deptCTE q1 INNER JOIN deptCTE q2 ON q1.id = q2.parent WHERE q1.parent IS NULL; The following execution plan …