Oracle connection Query

I have been confused about internal connections, left connections, left outer connections, right connections, right outer connections, and full connections. I have created two tables by myself, write an SQL statement to check whether the left connection and the left outer connection are the same, and the right connection and the right outer connection are the same. A guy once showed me what the left connection is like, and the left outer connection is

I have been confused about internal connections, left connections, left outer connections, right connections, right outer connections, and full connections. I have created two tables by myself, write an SQL statement to check whether the left connection and the left outer connection are the same, and the right connection and the right outer connection are the same. A guy once showed me what the left connection is like, and the left outer connection is

I have been confused about internal connections, left connections, left outer connections, right connections, right outer connections, and full connections. I have created two tables by myself, write an SQL statement to check whether the left connection and the left outer connection are the same, and the right connection and the right outer connection are the same. A guy once showed me what the left connection was like, and the left outer connection was like that. What I said was mysterious and confused. Test it by yourself and find that it is the same as that. It is more convincing to use the results.

Note: No left inner connection or right inner connection exists. (if the test is performed, an error is returned, indicating that these connections do not exist)

Create a student table

create table STUDENT(  ID      NUMBER(5),  NAME    VARCHAR2(20),  CLAZZID NUMBER(5))

Insert some records

Create a clazz table

create table CLAZZ(  ID   NUMBER(5),  NAME VARCHAR2(50))

Insert some records

Query the Student name and Class Name

-- Common mode. The connection mode is not specified. The select s is connected internally by default. id sid, s. name, c. id cid, c. name class name from student s, clazz c where s. clazzid = c. id; -- equivalent to select s. id sid, s. name, c. id cid, c. name class name from student s inner join clazz c on s. clazzid = c. id;

-- Left (outer) join. The left table is used as the base table. The number of records in the result set is equal to or greater than the number of records in the base table. select s. id sid, s. name, c. id cid, c. name class name from student sleft outer join clazz c on s. clazzid = c. id; -- or use left outer join, the results are the same -- available in oracle + select s. id sid, s. name, c. id cid, c. name class name from student s, clazz c where s. clazzid = c. id (+); -- + is located in clazz. student is used as the base table.

-- Right (outer) join. The right table is used as the base table. The number of records in the result set is equal to or greater than the number of records in the base table. select s. id sid, s. name, c. id cid, c. name class name from student sright join clazz c on s. clazzid = c. id; ---- or use right outer join, the results are the same -- available in oracle + select s. id sid, s. name, c. id cid, c. name class name from student s, clazz c where s. clazzid (+) = c. id; -- + indicates that the clazz is used as the base table.