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MySQL 高级SQL高级语句(二)
一.CREATE VIEW 视图 可以被当作是虚拟表或存储查询。 视图跟表格的不同是,表格中有实际储存数据记录,而视图是建立在表格之上的一个架构,它本身并不实际储存数据记录。 临时表在用户退出或同数据库的连接断开后就自动消失了,而视图不会消失。 视图不含有数据,只存储它的定义,它的用途一般可以简化复杂的查询。比如你要对几个表进行连接查询,而且还要进行统计排序等操作,写SQL语句会很麻烦的,用视图将几个表联结起来,然后对这个视图进行查询操作,就和对一个表查询一样,很方便。 语法:CREATE VIEW "视图表名" AS "SELECT 语句"; #定义视图 CREATE VIEW V_REGION_SALES AS SELECT A.Region REGION,SUM(B.Sales) SALES FROM location A INNER JOIN store_info B ON A.Store_Name = B.Store_Name GROUP BY REGION; #查看试图 SELECT * FROM V_REGION_SALES; #删除视图 DROP VIEW...
MySQL 高级SQL语句-CSDN博客
前言: MySQL 查询数据的执行过程 客户端向 MySQL 服务器发送一条查询请求,连接器负责处理连接,并进行身份验证和权限控制。 MySQL 先检查查询缓存,如果命中缓存,则立刻返回存储在缓存中的结果;否则使用查询解析器进行SQL语句解析、预处理,再由优化器生成对应的执行计划。 MySQL 根据执行计划,调用存储引擎来执行查询。 将结果返回给客户端,同时缓存查询结果。 创建两个表,并插入数据,作为操作对象 use mydb; create table location (Region char(20),Store_Name char(20)); insert into location values('East','Boston'); insert into location values('East','New York'); insert into location values('West','Los Angeles'); insert into location values('West','Houston'); create table store_info...
MySQL数据库高级查询语句_闲亦生花的博客-CSDN博客
基于这两个数据库表格来实现以下实验 use kgc; create table location (Region char(20),Store_Name char(20)); insert into location values('East','Boston'); insert into location values('East','New York'); insert into location values('West','Los Angeles'); insert into location values('West','Houston'); location 表格 +----------+--------------+ | Region | Store_Name | |----------+--------------| | East | Boston | | East | New York | | West | Los Angeles | | West | Houston | +----------+--------------+ create table...
MySQL 高级(进阶) SQL 语句
创建两表以供使用 use xue; create table location (Region char(20),Store_Name char(20)); insert into location values('East','Boston'); insert into location values('East','New York'); insert into location values('West','Los Angeles'); insert into location values('West','Houston'); create table Store_Info (Store_Name char(20),Sales int(10),Date char(10)); insert into Store_Info values('Los Angeles','1500','2020-12-05'); insert into Store_Info values('Houston','250','2020-12-07'); insert into Store_Info...
SQL-On-Hadoop: Hive - Part II – SQLServerCentral
Introduction All big data systems are not made equal, including SQL-on-Hadoop systems like Hive, Polybase and SparkSQL. All of these employ various distributed computing techniques. In this article we learned why it is critical to understand some of these techniques in other to make the right big data tool selections. In Part I of this series we learnt what gave rise to Hadoop and the need for SQL-on-Hadoop big data systems which was pioneered by Hive.
SQL-On-Hadoop: Hive - Part I – SQLServerCentral
Introduction In this new SQL-On-Hadoop series of articles, we will continue exploring the benefits of distributed computing using your SQL Skillsets. We will learn how to run interactive and batch SQL queries on structured and semi-structured Big Data stored on Hadoop and other file storage systems using HiveQL,T-SQL and other Structured query options like Spark SQL.
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