db2 query tuning

at this timeOpen log file discovery occurrence recordLater, you can only check the log file periodically to find the slow query statement.Attention:After finding the slow query statement, to confirm the slow query by repeatedly using the SELECT statement, note that only SELECT statements can be used, even if the original statement is delete or update, etc., also

slow query, is there a quantitative standard? Slow query definition A slow query is an SQL statement that executes longer than a slow query time. How to view slow query times [Plain]View Plaincopy Show variables like ' long_query_time '; You can display

Query performance tuning is a big topic, where the technology involved is very broad, but we can generally divide it into the following levels: 1. Reduce data access. The related technique is to create an appropriate index that converts time-consuming operations such as full table scans, index scans (scan), to index lookups (seek). Establish the correct index, can make the database

Label:ORACLE : --Time Turn string To_char (sysdate, ' Yyyymmddhh24miss ') --String Turn time Select To_date (' 20140701125751 ', ' Yyyymmddhh24miss ') from dual--2014-07-01 12:57:51 --Query table SELECT * FROM all_tables WHERE table_name = ' {0} ' --Query column SELECT Aa.table_name as Tableename, Aa.column_name as ColName, NVL (Bb.comments, aa.column_name) as Coldesc From ( SELECT TABLE_NAME, COLUMN_NAME,

ObjectiveIn the previous article, we analyzed how the query optimizer works, including: detailed operation steps of the query optimizer, analysis of filter conditions, optimization of index items, and other information.In this article we analyze the detection of several key indicator values in the course of our operation.These indicator values are analyzed to analyze the operation of the statement and to an

DB2 materialized view Mqts are based on a table defined by the query result, and the MQT contains data from one or more tables on which the MQT definition is based, and using MQTS can significantly improve the operation performance of the query. The views and mqts for the database are defined based on a query. The

In DB2, the sum function used to replace the count query is to calculate and sum the column values. The www.2cto.com count function accumulates the columns that meet the conditions and adds one when the conditions are met. The count function is commonly used to count the number of records meeting a certain condition. For example, count the number of boys in student in the student information table: [SQL] se

Database Tuning tutorial (2) Prepare slow query data and optimize Databases 1. Slow query found In the previous section, we talked about the definition of slow queries. This section describes how to create a large table and prepare data for slow queries. 2. Prepare slow query data To find slow queries, you must first

The paging query method for Oracle, SQL, and DB2 is different from that for paging query statements in Oracle and SQL, the following describes the differences between DB2 paging query and paging query in other databases. Oracle pa

Materialized query tables using MQTS (materialized query tables, MQTS) The definition of an MQT is based on the results of the query. Mqts can significantly improve the performance of queries. This tutorial introduces Mqts, Summary tables (summary table), and staging tables, and shows you how to create and use materialized q