Method for remove SQL inquiry statment constant condition

A query statement and condition technology, applied in special data processing applications, instruments, electronic digital data processing, etc., can solve problems such as inability to eliminate, tedious data processing, affecting database query speed, etc., to reduce processing overhead and avoid query processing. Effect

Active Publication Date: 2007-11-21
北京神舟航天软件技术股份有限公司
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  • Claims
  • Application Information

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Problems solved by technology

[0002] In daily applications, databases often need to process large-scale data. Query is an operation frequently used by users. A complex query statement will cause the database system to perform a large amount of tedious data processing. For example, the complexity of the WHERE condition can greatly affect the performance of the dat

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  • Method for remove SQL inquiry statment constant condition
  • Method for remove SQL inquiry statment constant condition
  • Method for remove SQL inquiry statment constant condition

Examples

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[0021] In the OSCAR database, the parser syntax analysis submodule converts the SQL query statement in the form of a string into a parse tree structure, and then the analyze semantic analysis submodule converts the parse tree structure into the internally recognized Query query tree structure, and different parts of the SQL statement Converted into each subtree of the query tree, then the Optimizer query optimization module optimizes the Query structure, generates an execution plan Plan, and submits it to the Executer executor module for execution to obtain the query results. The present invention is located in the rule-based optimization sub-module in the Optimizer module.

[0022] The method of the present invention includes three steps shown in Fig. 1: creating a linked list, merging the linked list and rewriting the query statement.

[0023] The present invention first converts both CHECK constraints and WHERE conditions into subtrees of the query tree. The expression tree str...

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Abstract

A method for removing off constant condition of SQL query statement includes setting up chain list, combining chain list and rewriting query statement for effectively removing off constant condition of SQL query statement on semantics grade so as to avoid unnecessary query treatments.

Description

technical field [0001] The invention relates to a method for rewriting an SQL query statement, in particular to a method for removing constant conditions existing in the SQL query statement by using a linked list. Background technique [0002] In daily applications, databases often need to process large-scale data. Query is an operation frequently used by users. A complex query statement will cause the database system to perform a large amount of tedious data processing. For example, the complexity of the WHERE condition can greatly affect the performance of the database. query speed. [0003] At present, the known database query optimization technologies cannot eliminate complex WHERE constant conditions at the semantic level, which leads to the need for query executors to use WHERE conditions for filtering when scanning each row of the table, thereby greatly increasing data processing overhead. If the query optimizer can eliminate some unnecessary WHERE conditions from th...

Claims

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Application Information

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IPC IPC(8): G06F17/30
Inventor 郭毅
Owner 北京神舟航天软件技术股份有限公司
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