what is mysql query

Preparation (two sheet t1,t2):Table T1:Mysql> select * from T1;+-------+---------+| t1_id | T1_name |+-------+---------+| 1 | T1_1 || 2 | t1_2 |+-------+---------+2 rows in Set (0.02 sec)Table T2:Mysql> select * from T2;+-------+---------+| t2_id |

When we enter data regardless of the case, for example: Enter AAA or AAA, AAA can query the same results, indicating that the query condition is not sensitive to case.Solution One:So I doubted the MySQL problem. Do an experiment: Use the client

Transferred from: http://blog.csdn.net/kevinlifeng/article/details/43233227Statement is their own study is not original, hope everyone support the original.SQL statement optimization and indexing1.Innerjoin and left connection, right connection, sub

From:http://www.cnblogs.com/xuxm2007/archive/2010/11/16/1878211.htmlSELECT * FROM table LIMIT 5;SELECT * FROM Issu_info limit 0,6Limit 0,6Here's the right one, showing the top 6.SELECT * FROM Issu_info limit 7, 6;Limit 7,6Starting from 8th, take 6

Today: Select*from table1 where to_days (Time field name) =to_days (now ());Yesterday: Select*from table1 where To_days (now ())-to_days (Time field name) Nearly 7 days: Select*from table1 where Date_sub (Curdate (), Interval 7 day) Nearly 30 days:

Basic QueryRemoval of duplicate records >select DISTINCT vend_id from the products;Paging >select * from the products LIMIT 5;>select * from the products LIMIT 0, 5;>select * from the Products LIMIT 5, 5;Sort (Descending) >select * from the products

#coding: Utf-8 ' Created on October 25, 2017 @author:li.liu ' import pymysqldb=pymysql.connect (' localhost ', ' root ', ' root ' , ' Test ', charset= ' UTF8 ') m=db.cursor () "Try: #a =raw_input (' Please enter SQL statement ' + ' \ n ') m.execute (

Data Preparation:To Create a table:CREATE TABLE students (ID int unsigned primary key auto_increment not NULL,name varchar ("default"),Age tinyint unsigned default 0,height Decimal (5,2),gender enum (' Male ', ' female ', ' shemale ', ' secrecy

Why query speed is slowBefore trying to write a quick query, we need to be clear that what really matters is response time. If you think of a query as a task, it consists of a series of subtasks, each of which consumes a certain amount of time. If

#group by #group by + group_concat () #group by + aggregate function #group by + have #group by(1) Meaning of GROUP by: Group The results of the query in 1 or more fields, with the same field values as a group(2) Group by can be

Federated QueriesSelectA.*, B.adress, B.name fromA, bwhereA.sbno=B.cdidOrder byA.sbno, A.stimeSelect a.a_id, A.a_name, b.b_name from a A, b a where a.b_id = b.b_id // Union query Insert intoTable1 (XX,YY,ZZ)SelectXx,yy,zz fromtable2;SelectAxx asID,

Poor query performance is due to access to too much data All columns are returned when a multi-table connection is made select * from sakila.actor inner join sakila.file_actor using(actior_id)inner join sakila.film using(film_id)where

A1, look for redundant records in the table, duplicate records are based on a single field (Peopleid) to determine the select * from Peoplewhere peopleid in (select Peopleid from people GROUP by Peopleid Having count (Peopleid) > 1) 2, delete

Today:SELECT * FROM table name WHERE to_days (Time field name) = To_days (now ());Yesterday:SELECT * FROM table name WHERE to_days (now ())-To_days (Time field name) 7 days ago:SELECT * FROM table name where Date_sub (Curdate (), INTERVAL 7 day) 30

Show variables like ' character% ';The results are as follows:+--------------------------+---------------------------------------------------------------+| variable_name | Value|+--------------------------+--------------------------------------------

1. Copy the following statements to the SQLYOG query bar/*!40101 SET NAMES UTF8 */;CREATE TABLE ' T_student ' (' ID ' double,' Stuname ' varchar (60),' Age ' double,' Sex ' varchar (30),' Gradename ' varchar (60));Insert INTO ' t_student ' (' IDs ',

From_unixtime () is the time function in MySQLDate is the parameter that needs to be processed (the parameter is a UNIX timestamp), can be a field name, or it can be a Unix timestamp stringThe following '%y%m%d ' is primarily the formatting of the

1. Query fields#查询所有字段#查询指定字段2. Querying a specified record (where condition expression)#比较#指定范围#指定集合#匹配字符#查询空值#带IN关键字的集合查询range Query #带BETWEEN and keyword#带LIKE的字符匹配查询#带AND | Multi-criteria query for or3. Further operation of the query

First, simple query1. Most simple query (check all data)Select * from table name Note: * represents all columns and does not represent all rowsExample: SELECT * FROM Test2. Querying a specified columnSelect column name, column name from table

http://zhangzhaoaaa.iteye.com/blog/1689412 reference: "MySQL Technology insider SQL Programming"SELECT DISTINCT From lefttablejoin On WhereGroup Bywith{cube| ROLLUP}HavingOrder byLimitProcessing order From On Join where GROUP BY