Partition Selection SELECT * FROM t4 WHERE region_code BETWEEN 3 AND 5; In both these cases, the  WHERE  clause is transformed by the optimizer into  WHERE region_code IN (3, 4, 5) . This optimization is used only if the range size is smaller than the number of partitions. Consider this statement: The range in the  WHERE  clause covers 9 values (4, 5, 6, 7, 8, 9, 10, 11, 12), but  t4 has only 8 partitions. This means that the  DELETE  cannot be pruned. Important DELETE FROM t4 WHERE region_code BETWEEN 4 AND 12; When a table is partitioned by  HASH  or  [LINEAR] KEY , pruning can be used only on integer columns. For example, this statement cannot use pruning because  dob  is a  DATE  column: However, if the table stores year values in an  INT  column, then a query having  WHERE year_col >= 2001 AND year_col <= 2005  can be pruned. Tables using a storage engine that provides automatic partitioning, such as the  NDB  storage engine used by MySQL Cluster can be pruned if they are explicitly partitioned. Explicit selection of partitions and subpartitions for rows matching a given  WHERE  condition is supported. Partition selection is similar to partition pruning, in that only specific partitions are checked for matches, but differs in two key respects: SQL statements supporting explicit partition selection are listed here: 24.5 Partition Selection 1. The partitions to be checked are specified by the issuer of the statement, unlike partition pruning, which is automatic. 2. Whereas partition pruning applies only to queries, explicit selection of partitions is supported for both queries and a number of DML statements. • LOAD XML • LOAD DATA . • UPDATE • REPLACE • INSERT • DELETE • SELECT Explicit partition selection is implemented using a  PARTITION  option. For all supported statements, this option uses the syntax shown here: The remainder of this section discusses explicit partition selection as it applies generally to the statements just listed, and provides some examples. 4708 SELECT * FROM t4 WHERE dob >= ’2001-04-14’ AND dob <= ’2005-10-15’;