hive query optimization

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A database query optimization method for database query optimization

,neibuyonghu,reader,title from Tgongwen where fariqi> ' 2004-1-1 ' and fariqi4. The date column will not slow down the query speed because there is a minute or seconds inputIn the following example, there are 1 million data, 500,000 data after January 1, 2004, but only two different dates, the date is accurate to the day, before the data 500,000, there are 5,000 different dates, the date is accurate to the second.Select Gid,fariqi,neibuyonghu,reader,t

Record Data Query Optimization and Data Query Optimization

Record Data Query Optimization and Data Query Optimization One day, the bricks were moving so hot that a call was suddenly called. The business department reflected that a function was very slow and it was simply unbearable. How slow is it? About 90 s. Is it suddenly slow? Or was it slow before? It was a little slow be

PostgreSQL query optimization: Query Condition Optimization 1 (condition classification)

In SQL, query conditions need to be divided into three types in the query optimization stage. The three types of conditions have different effects and can be converted to each other in some cases.First, describe the SQL statement execution steps, which can be divided into three steps: 1. Read the tuples in the table; 2. If join exists, join is started; 3. filter

MySQL query optimization from getting started to running (ii) database query Optimization Technology Overview

Tags: uniform having text get data BSP Execution plan calculations take advantage of specificFive optimization techniques 1. Query reuse refers to the use of the previous execution results as far as possible, in order to save the query calculation of the whole process of time and reduce resource consumption. At present, the q

Basic query optimization and sub-query optimization in Oracle database _oracle

deptno, avg (SAL) from EMP WHERE Deptno in (a) GROUP by Deptno; Efficiency will be higher than the following SELECT deptno, avg (SAL) from EMP WHERE Deptno in (a) GROUP by Deptno; Of course, if the filter conditions of a grouped query design group calculations, they can only be specified in the HAVING clause. 5. Sub-query optimization

SQL optimization--Query optimization technology classification

there are usually several ways to tune a database: 1) Manual tuning. The main reliance on people, inefficient, requiring the operator to fully understand the principle of common sense depends on, but also the application, database management system, operating system and hardware have a broad and deep understanding. 2) Case-based tuning . This paper summarizes the recommended configuration values of database parameters and the design of

MySQL query optimization and MySQL Optimization

MySQL query optimization and MySQL Optimization1. Introduction A good web application has excellent access performance. MySQL database is an integral part of web applications and an important part that determines their performance. Therefore, it is vital to improve MySQL performance. MySQL performance improvement can be divided into three parts, including hardware, network, and software. The hardware and ne

Optimization of sub-query conditions for Oracle query optimization

Tags: sel div weight span subquery query lag around 11gEnvironment: Oracle 11g The existing A and B tables are associated with the A01 field, and the data in table A is not available in B. SQL as follows Select Count (1 from (select A.*, (selectCount(1) from where b.a01=as fromwhere flag=0 Because flag is a virtual field, the index causes the SQL to execute particularly slowly, and the total number of 310W data is about 2 seconds. Use NOT exists t

Sort out the key points of Data Query Optimization in Oracle databases, and query oracle Data

Sort out the key points of Data Query Optimization in Oracle databases, and query oracle Data The most basic task of a database is to store and manage data. The only database feature that an end user can see is its performance: the speed at which the database processes the results of a specified query, and return the r

3.MySQL Optimization---Some small summary of single-table query optimization (non-indexed design)

Tags: query statement set server query ffffff its large data ash whereorganized from the Internet.Summary: The next one is query optimization. In fact, we all know that the query part is far greater than delete and change, so query

MySQL optimization-performance analysis and query optimization

MySQL optimization-performance analysis and query optimizationoptimization should be carried out throughout the product development cycle, such as when writing complex SQL to view the execution plan, when installing the MySQL server as reasonable as possible (see too much to completely use the default configuration installation), Choose a reasonable hardware configuration based on the application load. 1. P

SQL optimization----million data query optimization

= rcvlbes.customer_id and rcvblls.balance>0 ORDER by Cust.name Into TEMP cust_with_balance Then query in the temporary table in the following way: SELECT * from Cust_with_balance WHERE postcode> "98000" The rows in the staging table are less than the rows in the primary table, and the physical order is the required order, reducing disk I/O, so the query effort can be significantly reduced. Note: Changes to

Mysql nested query and Table query optimization methods

type: ALL means) and does not use any indexes. This is a scan of tens of thousands of rows of records on the table. In an external query, each row is queried once. Although no value is used in the query, the query is "optimized" to reference an external query. According to this analysis, the

Correct use of indexes (SQL optimization), limit paging optimization, execution plan, slow log query

records of the table is not suitable for direct use. A performance optimization method for limit paging problemSpeed up paged queries with table overlay indexesAs we all know, if you only include that index column (overwriting index) in the statement that uses the index query, then this will query quickly. Because the index is used to find the

SQL optimization----million data query optimization

cust_with_balanceThen query in the temporary table in the following way:SELECT * from Cust_with_balanceWHERE postcode> "98000"The rows in the staging table are less than the rows in the primary table, and the physical order is the required order, reducing disk I/O, so the query effort can be significantly reduced.Note: Changes to the primary table are not reflected when the staging table is created. When d

Mysql nested query and table query optimization method _ MySQL

Optimization Methods for mysql nested queries and table queries: bitsCN.com poor optimization of nested queries As mentioned above, join table queries are more effective than nested queries without special considerations. Although the two queries share the same meaning, even though your plan is to tell the server what to do and then let it decide how to do it, sometimes you have to tell it how to change it.

SQL statement and query optimization of MySQL database performance optimization

Optimization objectivesReduce IO timesIo is always the easiest place to bottleneck the database, which is determined by the responsibility of the database, most of the database operations over 90% of the time is occupied by IO operations, reducing IO times is the first priority in SQL optimization, of course, is the most obvious optimization method.Reduce CPU Com

Simple MySQL optimization tool-slow query and mysql optimization tool

Simple MySQL optimization tool-slow query and mysql optimization tool Slow Query First, enabling slow queries is a prerequisite regardless of the optimization. The slow query Mechanism records slow

Mysql nested query and Table query optimization method _mysql

Nesting Queries Poor optimization As I mentioned above, a table query is more efficient than a nested query, regardless of the particular situation. Although the two queries express the same meaning, although your plan is to tell the server what to do and then let it decide what to do, sometimes you have to tell it to change. Otherwise the optimizer might do some

Query optimizer for MySQL Query optimization series lectures _ MySQL

When you submit a query, MySQL will analyze it to see if some optimization can be done to make it faster to process the query. This section describes how the query optimizer works. If you want to know the optimization methods used by MySQL, you can refer to the MySQL Referen

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