Abstract: A method, apparatus, and article of manufacture for optimizing a query in a computer system, wherein the query is performed by the computer system to retrieve data from a database stored on the computer system. The optimization includes: (a) combining join predicates from a query with local predicates from each branch of one or more UNION ALL views referenced by the query; (b) analyzing the combined predicates; and (c) not generating the join when the analysis step indicates that the combined predicates lead to an empty result.

Abstract: A method, apparatus, and article of manufacture for optimizing a query in a computer system. During compilation of the query, a GROUP BY clause with one or more GROUPING SETS, ROLLUP or CUBE operations is maintained in its original form until after query rewrite. The GROUP BY clause with the GROUPING SETS, ROLLUP or CUBE operations is then translated into a plurality of levels having one or more grouping sets. After compilation of the query, a grouping sets sequence is dynamically determined for the GROUP BY clause with the GROUPING SETS, ROLLUP or CUBE operations based on intermediate grouping sets, in order to optimize the grouping sets sequence. The execution of the grouping sets sequence is optimized by selecting a smallest grouping set from a previous one of the levels as an input to a grouping set on a next one of the levels. Finally, a UNION ALL operation is performed on the grouping sets.

Abstract: A method and system for executing a query to access data stored in a database, wherein the query includes a plurality of DISTINCT keys, is disclosed. The method and system of the present invention includes providing a first DISTINCT operation on a first DISTINCT key, storing data fetched from the first DISTINCT operation in a master workfile if more than one sort process is needed to execute the query, and utilizing the master workfile to perform subsequent DISTINCT operations for the other DISTINCT keys.

Abstract: Provided is a method, system, and program for performing a cursor operation. A result table is generated including rows corresponding to a subset of rows in a base table having data in one or more columns that satisfy a query predicate clause. A command is received to perform a cursor operation with respect to a subject row in the result table. A lock is obtained on a row in the base table corresponding to the subject row in the result table. An operation specified in the received command is performed with respect to the subject row after obtaining the lock. The lock on the row in the base table is released after performing the operation.

Abstract: Disclosed is a system, method, and program for performing a join operation on a multi-column table and at least two satellite tables having a join condition. Each satellite table is comprised of multiple rows and at least one join column. Each multi-column table is comprised of multiple rows and at least one column corresponding to the join column in each satellite table. A join operation is performed on the rows of the satellite tables to generate a first join result comprising concatenations of the rows of the satellite tables. Less than all the concatenated rows in the first join result that satisfy the join condition are then selected. The selected concatenated rows in the first join result are then joined to the multi-column table.

Abstract: Provided is a method, system, and program for performing a cursor operation. A result table is generated including rows corresponding to a subset of rows in a base table having data in one or more columns that satisfy a query predicate clause. A command is received to perform a cursor operation with respect to a subject row in the result table. A lock is obtained on a row in the base table corresponding to the subject row in the result table. An operation specified in the received command is performed with respect to the subject row after obtaining the lock. The lock on the row in the base table is released after performing the operation.

Abstract: Disclosed is a method, system, and program for performing a join operation on a multi-column table and at least two satellite tables having a join condition. Each satellite table is comprised of multiple rows and at least one join column. The multi-column table is comprised of multiple rows and at least one column corresponding to the join column in each satellite table. A join operation is performed on the rows of the satellite tables to generate concatenated rows of the satellite tables. One of the concatenated rows is joined to the multi-column table and a returned entry from the multi-column table is received. A determination is then made as to whether the returned entry matches the search criteria. If so, a determination is made as to whether one of the satellite tables has duplicates of values in the join column of the returned matching entry or the multi-column table has duplicate entries in the join columns.

Abstract: An automatic charging system for charging nickel-metal-hydride batteries is presented. The battery charging system uses a method of detecting the lowest charge current to control its charging process. The system has a constant voltage power supply including a short-circuit protection device, a battery voltage detector, a current detector, a current to voltage converter, a voltage amplifier, an analog to digital converter, a single chip microcomputer, a capacity indicator, a time indicator and a full-charge indicator. The system uses a constant voltage to charge batteries with a floating current according to the quantity of the active ions in the batteries. The battery charge current is converted to a voltage signal which is then amplified and digitized. The microcomputer detects the digitized signal to estimate the magnitude of the charge current.