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- CTEs are declared at the beginning of a query, while subqueries are embedded within it.
- CTEs always require a name, although PostgreSQL is the sole database system mandating named subqueries.
- CTEs have the capability for recursive usage, which will be elaborated on later.
- CTEs typically offer superior readability in complex report composition compared to subqueries.
- A CTE can be referenced multiple times within a query, whereas a subquery is limited to a single utilization, potentially reducing query length without necessarily enhancing performance.
- Subqueries, unlike CTEs, can be employed in WHERE clauses alongside IN or EXISTS keywords.
- Subqueries facilitate the retrieval of specific data from one table to update values in another, a task not suited for CTEs.
- Certain functionalities are exclusive to subqueries, such as situations where a subquery is incorporated into a WHERE clause or utilized to fetch a singular value for updating another table. As mentioned earlier, these tasks cannot be accomplished using CTEs in SQL.