sql joins tutorial

[PHP code audit instance tutorial] SQL injection-1. the blog will update several PHP code auditing tutorials recently. the articles are reposted from a friend's blog. the style of the articles is concise and clear, and are similar to what I always stick to in my blog. The article has been authorized (cnbraid authorization), although not original, but the article is awesome, I hope my friends like it.0x01

SQL getting started Tutorial: SQL create table and database [create databse] The statement for creating a databaseThe create database statement is used to CREATE a DATABASE. SQL syntax for creating a database Create database database_nameThe example of creating a database is now that we need to create a database cal

SQL Getting Started Tutorial: SQL CREATE INDEX syntax The table in which the index statement is created to create the metric. Metrics allow database applications to find data quickly, without reading the entire table. IndexThe index can be built in a table to find data more quickly and efficiently. Users cannot see metrics, they are only used to speed up sear

"annual Salary"From EMP ORDER by 3 DESC;SELECT ename,job,sal from emp ORDER by Job,sal DESC;SELECT ename,job,sal from emp ORDER by Empno;Modify Default display widthSET line[size] {80|n}SET Line 100L display the SQL statement in the buffer you just enteredN Text modified section of error'/' (run) commandSAVEGET@ or Start command when the specified script file contents are loaded into the SQL buffer to runS

SQL statement concise tutorial for linux --- CREATE VIEW, concise tutorial --- create A View can be considered as a virtual table. Unlike a table, a table stores actual data, while a table is built on a table architecture and does not actually store data. The syntax for creating a view table is as follows: Create view "VIEW_NAME" AS "

Simple tutorial on SQL statements in linux --- UNION, simple tutorial --- union UNIONThe purpose of the command is to combine the results of two SQL statements. From this perspective,UNIONThis is somewhat similar to JOIN, because both commands can retrieve data from multiple tables.UNIONOne restriction is that the colu

Technical preparation Based on the SQL SERVER2008R2 version, a simpler case library (Northwind) of Microsoft is used for parsing. First, data connection Data connections are the most commonly used when we write T-SQL statements, and we get the data we want through the association of two tables. SQL Server supports three physical connection operators by defaul

A concise tutorial on SQL statements in linux --- UNION ALL, a concise tutorial --- union UNION ALLThe purpose of this command is to combine the results of two SQL statements.UNION ALLAndUNIONThe difference is thatUNION ALLEach qualified item is listed, regardless of whether the item value is repeated. UNION ALLSyntax:

Simple tutorial on SQL statements in linux --- primary key, foreign key, and SQL Primary Key)Each item in is a unique value in the table. In other words, it is used to uniquely identify each row of data in a table. A primary key can be a column in the original data, or a column created by a person (a column irrelevant to the original data ). A primary key can con

SQL Getting Started Tutorial: SQL AVG () function AVG () functionAVG () function returns the average value of the values column.AVG () syntax for the database SELECT AVG (column_name) from table_name Let's look at a table first. _id orderdate orderprice customer 1 2008/11/12

Linux SQL statement concise tutorial --- HAVING, concise tutorial --- having How can we set conditions for the values produced by functions? For example, we may only need to know which stores have a turnover of more than $1,500. In this case, we cannot useWHERE. What should we do? Fortunately, SQL providesHAVINGAnd we

Simple tutorial for SQL statements in linux --- CREATE TABLE, simple tutorial --- create A table is the basic architecture for storing data in a database. In most cases, the database vendor cannot know how to store your data. Therefore, you usually need to create tables in the database. Although many database tools allow you to create tables without using

SQL getting started Tutorial: SQL CREATE INDEX syntax The table used to create the index in the create index statement. Indicators allow database applications to quickly find data without reading the entire table. MetricsThis index can be created in a table to find data faster and more effective. Users cannot see indicators. They are only used to speed up sea

SQL Beginner Tutorial: Select top Use tutorial OK, let's take a look at the syntax in select Top. such as Mssql:select top from table_name In Mysql:select * FROM table_name limit 0,10 SELECT Top Number|percent column_name (s) from table_name Let's take a look at an example tutorial. _id LastName

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SQL statement concise tutorial for linux --- DISTINCT, concise tutorial --- distinct SELECTThe command allows us to read all the data in one or more columns of a table. This will capture all the data, regardless of whether the data value is repeated or not. In data processing, we often encounter different data values in the table. In other words, we nee

[PHP code audit instance tutorial] SQL injection-2. global protection Bypass UrlDecode 0x01 background Currently, WEB programs basically have global filtering for SQL injection, such as enabling GPC in PHP or common in global files. use the addslashes () function on php to filter the received parameters, especially single quotes. In this case, we need to find som

essentially unused.Mysql> SELECT * FROM student NATURAL JOIN class;+----+------+-----+---------+-------+| ID | name | Age | ClassId | CNAME |+----+------+-----+---------+-------+| 1 | S1 | | 1 | Class One | | 2 | S2 | | 1 | Class II | | 3 | S3 | | 2 | | +----+------+-----+---------+-------+3 rows in SetYou can see that there is only one column ID, because student is automatically merged with the same ID column in Class Two table, which is equivalent to the

[PHP code audit instance tutorial] SQL injection-4. global protection Bypass second injection 0x01 background Currently, WEB programs basically have global filtering for SQL injection, such as enabling GPC in PHP or common in global files. use the addslashes () function on php to filter the received parameters, especially single quotes. Secondary injection is als

Simple tutorial on SQL statements in linux --- CREATE INDEX, simple tutorial --- create Index helps us quickly find the required information from the table. For example, suppose we want to find a message in a gardening book about how to plant green peppers. If this book does not have an index, we have to read it from the beginning until we find something about th