sql full outer join

From: http://www.williamlong.info/info/archives/50.html In a formal database environment, we often encounter this situation: the required data is not stored in the same data table. At this time, you need to use join. Of course, how to combine the data of different databases depends on how you use it. There are four different Join methods, in this article, we will introduce you to inner

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.studentid Iv. fully connected-full join: Using the format as above has been explained above Remove the data from the left and right two tables, whether or not they match: Select S.name,m.mark from student s

table in the associated result set row are null (NULL).(2) SQL statement:SELECT *From table1 left join table2 on Table1.id=table2.id-------------Results-------------ID Name ID Score------------------------------1 Lee 1 902 Zhang 2 1004 Wang Null NULL------------------------------NOTE: All clauses that contain table1, return table2 corresponding fields according to specified criteria, non-conforming null di

is called the OUTER join Or take the above data sheet for example, list all the orders, and the person who ordered them-if any SELECT Persons.lastname, Persons.firstname, Orders.orderno from Persons right JOIN Orders on persons.id_p =orders.id_p ORDER by Persons.lastname Result set: LastName FirstName OrderNo Adams

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 formalized database environment, we often encounter

Full (outer) join is the syntax used to fully connect two tables. That is to say, if you want to associate Table A with table B, you can obtain records that exist in Table A but not in Table B, or that exist in Table B but not in table. The on clause is used to determine whether the record exists. The following is an example:

Label:--Build Table Table1,table2:CREATE TABLE table1 (ID int,name varchar (10))CREATE TABLE table2 (ID int,score int)Insert INTO table1 Select 1,leeInsert INTO table1 Select 2,zhangInsert INTO table1 Select 4,wangInsert INTO table2 Select 1,90Insert INTO table2 Select 2,100Insert INTO table2 select 3,70such as table-------------------------------------------------Table1 | table2 |-------------------------------------------------ID Name |id Score |1 Lee | 90 |2 Zhang 100 |4 Wang |3 70 |---------

two results were met, and the results were as follows: Second, left join connect-left join: Left join is to select all the tuples from the left table: Select S.name,m.mark from student s left join Mark M on S.id=m.studentid The above statement is the left side of the table, that is, the tuple in the student table is

-right join: The right 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.studentid The 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-

: The right 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.studentid The 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

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; //INNER JOIN varquery = fromSinchdb. Students

SQL table join query (inner join, full join, left join, right join) Prerequisites: Assume that there are two tables, one is the student table and the other is the student renewal table

, teacher) (4, principal)Internal connection results:Select a.*,b.* from A inner join B on a.id=b.id;1 31 students2 Li 42 TeacherLeft JOIN Connection results:Select a.*,b.* from A left join B on A.id=b.id;1 31 students2 Li 42 Teacher3 Harry NULL NULLRight Join Result:Select a.*,b.* from A right