1. First, prepare two lists
Sector Table:
Employees table:
The following table we have these two different connection operation
1. the connector
Role: Query two tables of common parts
语句：Select <select_list> from tableA A Inner join tableB B on A.Key = B.Key
Example: SELECT * from employee e INNER JOIN department d on e.dep_id = d.id;
The results showed: with this method to find, as we have not found id data 8
2. Left connection
Role: the contents of the left side of the table all found the right table only identify records satisfy the condition
语句：Select <select_list> from tableA A Left Join tableB B on A.Key = B.Key
示例：SELECT * from employee e LEFT JOIN department d on e.dep_id = d.id;
The results show:
3. The right connection
Role: the contents of the table to the right of all identified, left the table only identify records satisfy the condition
语句：Select <select_list> from tableA A Left Join tableB B on A.Key = B.Key
Example: SELECT * from employee e RIGHT JOIN department d on e.dep_id = d.id;
The results showed that:
4. Query left table unique data
Role: A unique data query of
语句：Select <select_list> from tableA A Left Join tableB B on A.Key = B.Key where B.key IS NULL
Example: SELECT * from employee e LEFT JOIN department d on e.dep_id = d.id WHERE d.id IS NULL;
The results showed that:
5. Query exclusive right table data
Role: A unique data query B,
语句：Select <select_list> from tableA A Right Join tableB B on A.Key = B.Key where A.key IS NULL
示例：SELECT * from employee e RIGHT JOIN department d on e.dep_id = d.id WHERE e.id IS NULL;
The results show:
6. fully connected
Role: query all the information two tables
语句：Select <select_list> from tableA A Full Outter Join tableB B on A.Key = B.Key
Note: Mysql default does not support this wording Oracle support can be used to connect the left and right connections to work together as a full connection
Example:
SELECT * from employee e LEFT JOIN department d on e.dep_id = d.id
UNION
SELECT * from employee e RIGHT JOIN department d on e.dep_id = d.id
The results show:
7. queries about their unique data table
Role: A and B each query unique data
语句：Select <select_list> from tableA A Full Outter Join tableB B on A.Key = B.Key where A.key = null or B.key=null
示例：
SELECT * from employee e LEFT JOIN department d on e.dep_id = d.id WHERE d.id is NULL
UNION
SELECT * from employee e RIGHT JOIN department d on e.dep_id = d.id WHERE e.dep_id is NULL
The results show:
