Optimization of nested SQL queries revisited
SIGMOD '87 Proceedings of the 1987 ACM SIGMOD international conference on Management of data
Why decision support fails and how to fix it
ACM SIGMOD Record
SQL query optimization: reordering for a general class of queries
SIGMOD '96 Proceedings of the 1996 ACM SIGMOD international conference on Management of data
Outerjoin simplification and reordering for query optimization
ACM Transactions on Database Systems (TODS)
An overview of data warehousing and OLAP technology
ACM SIGMOD Record
On optimizing an SQL-like nested query
ACM Transactions on Database Systems (TODS)
Fundamentals of Data Warehouses
Fundamentals of Data Warehouses
Data Cube: A Relational Aggregation Operator Generalizing Group-By, Cross-Tab, and Sub-Total
ICDE '96 Proceedings of the Twelfth International Conference on Data Engineering
Improved Unnesting Algorithms for Join Aggregate SQL Queries
VLDB '92 Proceedings of the 18th International Conference on Very Large Data Bases
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MySQL is an OLTP system without the ability to handle SQL subqueries. As part of our project in query optimization, we add subquery processing to MySQL through rewriting. First, we incorporate the ability to handle subqueries in the FROM clause; then rewrite queries with subqueries in the WHERE clause by moving the subquery to the FROM clause and introducing suitable conditions to link the subquery and the main query tables. The result is a complete and correct unnesting procedure for SQL queries. The idiosyncrasies of SQL semantics make some rewritings tricky. While optimization issues are not directly addressed, the rewriting opens up the possibility of more efficient query processing in several cases.