1. What’s the difference between a single-row subquery and a multiple-row subquery? 2. What comparison operators are required for multiple-row subqueries? 3. What happens if a single-row subquery retu…
1. What’s the difference between a single-row subquery and a multiple-row subquery?
2. What comparison operators are required for multiple-row subqueries?
3. What happens if a single-row subquery returns more than one row of results?
4. Which SQL clause(s) can’t be used in a subquery in the WHERE or HAVING clauses?
5. If a subquery is used in the FROM clause of a query, how are the subquery’s results referenced in other clauses of the query?
6. Why might a MERGE statement be used?
7. How can Oracle 12c determine whether clauses of a SELECT statement belong to an outer query or a subquery?
8. When should a subquery be nested in a HAVING clause?
9. What’s the difference between correlated and uncorrelated subqueries?
10. What type of situation requires using a subquery?
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