join integrations

Take a look at the results of the left join and the right join with the Inner join and the full join to manipulate the table. Create a new two table in the database and insert the data you want to test. New table:[SQL]View PlainCopy Use [Test] GO /****** object: Table [dbo].[ EMP] Script Date: 06/

1. Inner join(Typical join operations use comparison operators such as = or The inner join uses the comparison operator to match rows in two tables based on the values of the columns in each table. For example, retrieve all rows with the same student ID in the students and courses tables.2. Outer Join.Outer Join can be

Join has a total of four internal and external Join inner join Left join Outer Join Right join Outer Join Full join Outer

Internal ConnectionINNER Join (equivalent connection):Only rows that are equal to the junction fields in two tables are displayed. This is the same effect as using Select to query multiple tables, so it is seldom used;External connection:Left JOIN: Displays all records in the left table on a left table basis, regardless of whether they match the association criteria, and the data in the right table shows on

I. Concepts 1. Cross join)Without the WHERE clause, it returns the Cartesian product of the two joined tables, and the number of rows returned is equal to the product of the number of rows in the two tables.For example:A: select a. *, B. * From Table1 A, Table2 B where a. ID = B. IDB: Select * From Table1 a cross join Table2 B where a. ID = B. IDIt is generally not recommended to use methods A and B, becaus

Label:Test Table SQL statementCreate TableA (IDintUnsigned not NULL Primary Keyauto_increment, nameChar( -) not NULL default "') Engine=MyISAMdefaultCharSet=UTF8;Create TableB (IDintUnsigned not NULL Primary Keyauto_increment, nameChar( -) not NULL default "', a_idint not NULL) Engine=MyISAMdefaultCharSet=UTF8;Insert intoAValues(NULL,'Zhang San'),(NULL,'John Doe'),(NULL,'Harry');Insert intoBValues(NULL,'Tom',1),(NULL,'Jack',2),(NULL,'Wally',1),(NULL,'Joan',4);Table results:Table A. Table BINN

--1.left Join left table is the primary table, left table returns all data, and the right table only returns data that matches the left table.Select T1.fpdm,t1.fphm, T1.ZJR,T1.ZJSJ,T1.ZJJX,T1.ZJJE,T1.ZFLX,T1.ZFID,T2.FPDM,T2.FPHM,T2.ZFLX from YW_ZJFPJL t1Left join XXDZMX T2 on t2.fpdm| | t2.fphm=t1.fpdm| | T1.fphmSelect T1.fpdm,t1.fphm, T1.ZJR,T1.ZJSJ,T1.ZJJX,T1.ZJJE,T1.ZFLX,T1.ZFID,T2.FPDM,T2.FPHM,T2.ZFLX f

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, that is, left OUTER joins, right connection, OUTER join, full OUTER join, the following is a

1 LEFT JOIN: The query results are based on the left table data. If the left table has four data, the right table has three data, the query result is four, and all the data in the left table.For example:EMP Table:Sal table:Left connection Select * from EMP left join SAL on EMP. ename = SAL.ename; Left JOIN, the table EMP is the primary table, so the q

Tags: style blog c http a widthFor SQL joins, learning may be a bit confusing. We know that the join syntax for SQL has a lot of inner, outer, left, and sometimes it's not very clear what the result set looks like for a select. There is an article on Coding horror that explains the join of SQL through the Venn diagrams of the Venturi diagram. I feel clear and understandable, turn around.Let's say we have tw

? The connection conditions can be specified in the from or where clause. We recommend that you specify the connection conditions in the from clause. The where and having clauses can also contain search conditions to further filter the rows selected by the connection conditions. Connections can be divided into the following types: Internal Connection.(Typical join operations use comparison operators such as = or Equal connection and natural connectio

Table A records the following: Aid anum 1 a20050111 2 a20050112 3 a20050113 4 a20050114 5 a20050115 Table B records the following: Bid bname 1 2006032401 2 2006032402 3 2006032403 4 2006032404 8 2006032408 The experiment is as follows: 1. Left join The SQL statement is as follows: Select * from Left join B On a. Aid = B. Bid The result is as follows: Aid anum bid bname 1 a20050111 1 2006032401 2 a20050112

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

Reprinted from: http://www.cnblogs.com/still-windows7/archive/2012/10/22/2734613.htmlPrerequisites: Suppose there are two tables, one is the student table and the other is the Student score table.The table data are:One, internal connection-inner jion:The most common connection query may be that of identifying the student's name and score:Select S.name,m.mark from student S,mark m where S.id=m.studentidThe above is our most common inner join, that is,

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

Various joins in MySQL 1. Cartesian Product (cross join) In MySQL, you can think of cross join or omit cross as join, or use ',' For example Select * From Table1 cross join Table2 Select * From Table1 join Table2 Select * From Table1, Table2 Because the returned result is

The join syntax is as follows: select [field] from [Table Name 1] inner/left/right/full join [Table name 2] on [Table Name 1. field 1] [Table name 2. field 2] cross join: the product of the flute. without any constraints, the number of rows in a table is multiplied by the number of rows in another table. Left join: re

This connection is often used in early query statements, which is a small problem. Therefore, I checked the information and summarized it as follows: External connections are easier to understand,A. It is generally used in some classification codes. For example, if you have an employee information table, the position information isCodeAnd the meaning of this Code is described in the position table.B. Classified information storage. For example, in the preceding employee information table, the

A. = Eg. Select a. a B. B from a, B where a. A = B. A and A. C = 'herengang '; Under this condition, it only shows the data that a. A = B. A and A. C = "herengang ". Although it there is data which. C is "herengang", but if we can't find such record which. A value equals to. A in Table B, then it will be cleared. B. Left join Select a. a, B. From Table Left join Table B On a. A = B. A and A. C = "herengang"

Inner JOIN (equivalent connection) returns only rows that have the same join field in two tablesLeft join returns records containing all the records in the left table and the equivalent of the junction fields in the right tableRight join returns records that contain all the records in the right table and the same