PostgreSQL全外连接 FULL OUTER JOIN
postgresql 全外连接 FULL OUTER JOIN
全外连接从左表和左表中返回所有行。 它将NULL置于不满足连接条件的位置。
语法:
SELECT table1.columns, table2.columns
FROM table1
FULL OUTER JOIN table2 ON table1.common_filed = table2.common_field;
如图:
实例数据:
表一:EMPLOYEES
表二:DEPARTMENT
执行全外连接 :
SELECT EMPLOYEES.ID, EMPLOYEES.NAME, DEPARTMENT.DEPT
FROM EMPLOYEES
FULL OUTER JOIN DEPARTMENT ON EMPLOYEES.ID = DEPARTMENT.ID;