explain gigabytes

India's Java programmer Shekhar Gulati posted "How I explained mapreduce to my wife?" on his blog ?" This article describes the concept of mapreduce. The translation is as follows:Huang huiyu. Yesterday, I gave a speech about mapreduce in xebia's office in India. The speech went smoothly and the audience were able to understand the concept of mapreduce (based on their feedback ). I was excited to explain the concept of mapreduce to technical audiences

Explain shows how MySQL uses indexes to process select statements and connect tables. It can help you select better indexes and write more optimized query statements.You can add the explain statement before the SELECT statement:Example: Explain select surname, first_name Form A, B where a. ID = B. IDThe analysis result is as follows:TableTypePossible_keysKeyKey_l

Please explain the meaning of the code in one sentence. Header (X-Powered-By: ThinkPHP); this is a piece of code in thinkphp. I don't know what it means. please explain it. Thank you. ------ Solution -------------------- information about X-Powered-By will appear in HTTP Status nbsp; let others know that you have developed it using the ThinkPHP framework ------ the solution can

Description in mysql: MySQLexplain BitsCN.com The usage of explain in mysql has recently encountered some database problems during performance tests. Generally, you can use slow query logs to find SQL statements with poor execution performance, however, it is not possible to find these SQL statements. we need to help developers analyze the problem. this often uses explainexplain to show how mysql uses indexes to process select statements and connect t

popular public key algorithm at present.RSA security is based on the difficulty of large number decomposition. Its public and private keys are functions of a pair of large prime numbers (100 to 200 decimal digits or larger). The difficulty of recovering plaintext from a public key and ciphertext is equivalent to decomposing the product of two large primes (which is an accepted mathematical problem).The RSA's public key, the private key's composition, and the encrypted, decrypted formula are vis

Explain shows how MySQL uses indexes to process SELECT statements and join tables. Can help select better indexes and write more optimized query statements. Using the method, add explain to the SELECT statement. EXPLAIN Explanation of the column: column Description Table Shows which table the data for this row is

The usage of explain in MySQL recently encountered some database problems in performance testing, often using slow query log to find the execution of poor performance of SQL, but only to find these SQL is not possible, we need to help developers to analyze the problem, This often uses Explainexplain to show how MySQL uses indexes to process SELECT statements and join tables. Can help select better indexes and write more optimized query statements. Us

1 showshow tables; Show all tables of the database show databases ; for [email protected]; View the permissions of the current user show index from table; View the indexes of the current table definition2 Describe getting information about columnsThe Replace function of show columnsDescribe table;describe columns;3 Explain understanding the work process of the query1) explain tables; The Direct query tab

Tags: mysql explainReference: http://www.2cto.com/database/201307/230048.htmlhttp://blog.csdn.net/zhuxineli/article/details/14455029Explain is used to analyze how MySQL uses indexes to process SELECT statements and join tables. Can help select better indexes and write more optimized query statements.1. IDThe order of execution of the statement is identified. Refers to the order in which SELECT statements are executed2, Select_type:2.1. Simplesimple Type, as long as there is no subquery or union

　　explain shows how MySQL uses indexes to process SELECT statements and join tables. can help select better indexes and write more optimized query statements .1. Create a databaseThe SQL statements are created as follows:/*Navicat MySQL Data Transfer source Server:localhost-newpassword source Server version:50550 Source Host : localhost Source database:testexplain Target Server version:50550 File encoding:utf-8 Date: 08/05/2016 18:06:12 PM*/SETNAMES

Tags: specify mongod tag query 9.png Note style scan imaMongoDB Analyzer: To detect if the MongoDB parser is open: Db.getprofilinglevel () 0 indicates no open 1 means open, and if the query execution time exceeds the maximum query execution time for the second parameter in milliseconds (ms), it is logged or ignored. 2 means open, and all query statements are logged Db.setprofilinglevel (2) A System.profile collection is found in the test database at this point: but thi

1. Use the explain statement to view the results of the analysis, such asSelect * from Test1 where id=1;will appear:ID selecttype table type possible_keys key Key_len ref rows Extrawhich Type=const indicates that it was found once through the index. Key=primary, indicates that a primary key is used Type=all indicates full table scan Key=null indicates that the index is useless Type=ref because this is considered to be mo

Use of the 1.explain plansql> explain plan for delete from T_jingyu; Explained.sql> select * FROM table (dbms_xplan.display); Plan_table_ OUTPUT------------------------------------------------------------------------------------------------------------------- -------------------------Plan Hash value:1368587462------------------------------------------------------------- ----------| Id | Operation | Name | R

Tags: Explain disk information retrieval LAN output file property commit ScanReproduced from http://blog.sina.com.cn/s/blog_4586764e0100o9s1.html useexplainStatement to see the results of the analysis asExplain select * from Test1 where id=1;will appear:ID selecttype Table Type possible_keys key Key_len ref rows extra Columns wherein, type=const means that through the index once found, key=primary words, the use of the primary key Type=all, expressed

Explain shows how MySQL uses indexes to process SELECT statements and join tables. Can help select better indexes and write more optimized query statements.Using the method, add explain to the SELECT statement:Such as: Explain select surname,first_name form a b where a.id=b.id Explanation of the Explain

Mysql --- functions of index and explain MySQLexplain Mysql explain uses explain SQL statements to help you select better indexes and write more optimized query statements. Of course, if you use like '% username %', the index will not be used. you only use like 'username % 'to use the index. of course, for common The explain