difference between inner join and outer join

First, the concept 1. Left join the left outer join To the left table, go to the right table to find the same field, if more than one will be listed in sequence 2. Connect Join Find the same records around the same 3. Fully connected full outer

simple because it is a left join, explained below: We know that the logic of the left join is a table or that the data in the primary table will appear in the final result set, so what does the "a.isdel=0" condition play in the process of the LEFT JOIN in statement 3? The function is that the system in the left joint, the first in a table with "a.isdel=0" condit

Label: Similarly, using the goods table to practice subqueries, the table structure is as follows: All data (cat_id associated with category.cat_id): Category table: Mingoods (test when connecting queries) First, sub-query 1,where sub-query: The result of the inner query as the comparison condition of the outer query 1.1 One item with the largest query ID (implemented using sort + paging) :mysql> SELEC

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 |---------

columns in the connected table, including duplicate columns, are listed in the query results. 2. Unequal join: Use a comparison operator other than the equal operator to compare the column values of the connected columns. These operators include >,>=, 3. Natural join: Use the equal to (=) operator in the connection condition to compare the column values in the connected column. However, it uses the select

Inner join There are two tables A and B. The structure of Table A is as follows: Aid: int; identifies the seed, primary key, and auto-increment ID Aname: varchar The data, that is, the records from select * From A, are shown in 1: Figure 1: data in Table Table B has the following structure: Bid: int; identifies the seed, primary key, and auto-increment ID Bnameid: int Data, that

based on WHO, and only records meeting the conditions are displayed.--------------------------------------------Note:The left join operation is used to combine records of the source table in any from clause. Use the left join operation to create a left Outer Join. The outer

1. Internal Connection is simpleSelect a. *, B. * from a, B where a. ID = B. IDSelect a. *, B. * from a inner join B on A. ID = B. IDThe above two statements are completely equivalent. 2. left Outer JoinSelect * from EMP a left join dept D on A. deptno = D. deptnoSelect * from emp a, DEPT d Where a. deptno = D. deptno

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"

2006032402 3 a20050113 3 2006032403 4 a20050114 4 2006032404 Null null 8 2006032408 (The number of affected rows is 5) Result description: After careful observation, we will find that the result of left join is exactly the opposite. This time, it is based on the right table (B) and is filled with null when table A is insufficient. 3. Inner join The SQL stateme

data in both tables is displayedLeft join: Understood to be "there is display", such as on A.field=b.field, displays all the data present in table A and the data in A and B, the data in A and B does not appear as nullRight join: Understood to be "show on display", such as on A.field=b.field, displays all the data present in table B and the data in A, B, and the data in B that is not in a, null displayFull

connection A and B table is the same as the result of the left coupling B and a, which means: Select A.name B.name from the left of Join B on A.id=b.id And the result of the execution of the select A.name b.name from B right Join A is the same. 3. Full join: Takes out all records of a joined field in two tables to form a recordset's

The following articles mainly describe the table connection statements for Oracle Outer join and cross join. Oracle database connections include the inner join statements) oracle Outer join