difference between inner join and outer join

desired results First, remove the foreign key of the products data table. Otherwise, a new supplierid in the products data table does not have a record mapped to the suppliers data table, to understand the constraint of a data table, you can execute the SQL built-in sp_helpconstraint, which is executed in QA. Sp_helpconstraint Products Next, delete the foreign key fk_products_suppliers. Alter table Products Drop constraint fk_products_suppliers A new record is added to the products table. The s

products data table does not have a record mapped to the suppliers data table, to understand the constraint of a data table, you can execute the SQL built-in sp_helpconstraint, which is executed in QA. Sp_helpconstraint Products Next, delete the foreign key fk_products_suppliers. Alter table Products Drop constraint fk_products_suppliers A new record is added to the products table. The supplierid uses 50 because it is not mapped to the suppliers table. Insert into products (productname, supplie

connection is to remove all data from the right table, regardless of whether the table on the left has matching data:Select S.name,m.mark from student s right join Mark M on S.id=m.studentidThe above statement takes all the data from the Mark score table, regardless of whether there is a data match in the student table, as shown in:Iv. fully connected-full join:Remove the data from the left and right two tables, whether or not they match:Select S.nam

Test table:EMP Table Sal TableLeft JOIN: Results All rows are displayed in the table, and the right table determines that the column is the same as the left.SELECT * FROM EMP left join SAL on EMP. ename = SAL. ename; Right join: Results All rows are displayed in the table on the left, the table on the right is consistent with the tableSelect * from EMP right

(primary table) and the SAL (schedule) information related to EMP. Right connect [SQL] view plain copy Select * from EMP right join SAL on EMP. ename = SAL.ename; Right connection, table Sal is the primary table, so the query results show all the information of the salt (the primary table) and the EMP (schedule) and the information that Sal wants to close. Internal connection [SQL] view plain copy SELECT * FROM

information of the EMP (primary table) and the SAL (schedule) information related to EMP. Right-connect the Select * from emp to ' join SAL on EMP '. ename = SAL.ename; Right connection, table Sal is the primary table, so the query results show all the information of the salt (the primary table) and the EMP (schedule) and the information that Sal wants to close. Internal Connection

main table, So the result of the query is to display all the information of the EMP (main table) and the SAL (schedule) information related to the EMP. Right connect [SQL] view plain copy Select * from EMP right join SAL on EMP. ename = SAL.ename; Right connection, table Sal is the primary table, so the query results show all the information of the salt (the primary table) and the EMP (schedule) and the information that Sal wa

Label:Simply and clearly, connect to the inner and outer links. Suppose there are two tables of A and B Internal connection: Inner JOIN indicates that the record of the AB table is displayed, excluding the condition of the AB table . There are three kinds of outer joins, tha

Label:Original: http://blog.csdn.net/shadowyelling/article/details/7684714Left Join: Returns all the information in the table on the right and the information related to the left table conditionRight Join: Returns all of the information in the table in the list and information about the right table condition in the left tableInner Join: Returns information common

to (=) operator in the connection condition to compare the column values in the connected column. However, it uses the selection list to indicate the columns included in the query result set, delete duplicate columns in the connection table.For example, the following uses equijoin to list authors and publishers in the same city in the authors and publishers tables: Select *From authors as a inner join pub

Resolution: inline, left outer, right outer, full join, Cross join difference bitsCN.com Connections include: internal connection, external connection, and cross connection.I. inner connection-the most commonDefinition:Only the ro

of course join how to combine the data of different database, also depends on how you use it, there are four different ways of join, in this article we will introduce you Inner join and Outer join and its application. In a formal

The meaning of join is like the English word "join", connecting two tables, roughly divided into inner connection, outer connection, right connection, left connection, natural connection. The description here is to throw out a rotten picture and insert the test data.First of all, the classification (

Code is as follows: Copy code SELECT * FROMInner join BON a. aID = B. bID Equivalent to the following SQL statement: The Code is as follows: Copy code SELECT *FROM a, BWHERE a. aID = B. bID The result is as follows:AID aNum bID bName1 a20050111 1 20060324012 a20050112 2 20060324023 a20050113 3 20060324034 a20050114 4 2006032404 Result description:Obviously, only the records of A. aID = B. bID are di

Let's look at one of the simplest inner joins, inner the corresponding class information from the Join Class table when reading the student table:Static voidMain (string[] args) { using(varwriter =NewStreamWriter (Watchsqlpath,false, Encoding.UTF8)) { using(Dbappdatacontext db =NewDbappdatacontext ()) {db. Log=writer; //

} {1} {2}", item.ClassID, item.ClassName, item.Student.Name); } } } Console.ReadLine();} During Outer join, the joined table must be into a new variable gc, and gc. DefaultIfEmpty () is used to represent the Outer join. Additional notes related to linq to SQL: 1. Starting from CUD, how to insert

An inner join connects only matching rowsThe left OUTER join contains all rows from the table on the left (regardless of whether there are rows in the right table that match them), and all rows in the right tableA LEFT join B is equivalent to a left

* from a LEFT join B on aid= bid and aid>3, return　　　　If a select * from a LEFT join B on aid= bid where aid>3　　　　Because a temporary table is generated when executing such a statement, the condition in the on in this temporary table is not necessarily true, because it is possible that the field value is null.When a temporary table is generated, it is filtered according to the Where condition, so the condi

are as follows:AID Anum BID bname1 a20050111 1 20060324012 a20050112 2 20060324023 a20050113 3 20060324034 a20050114 4 2006032404 Result Description:Obviously, only a.aid = B.bid records are shown here. This shows that inner join is not based on who, it only shows records that match the criteria.--------------------------------------------Note:The left JOIN oper

Result Description:Obviously, only a.aid = B.bid records are shown here. This shows that inner join is not based on who, it only shows records that match the criteria.--------------------------------------------Note:The left JOIN operation is used to combine records from the source table in any from clause. Use the left JOIN