SQL/DB Essentials - CH08

JOINメッセージの整理

SELECT t1.c1, ..., t2.c2, ...
FROM t1 LEFT|RIGHT|FULL [OUTER] JOIN t2 ON t1.c1 = t2.c2
WHERE 검색조건 ;

SELECT t1.c1, ..., t2.c1, ...
FROM t1 LEFT|RIGHT|FULL [OUTER] JOIN t2 USING (c1)
WHERE 검색조건 ;

SELECT emp.employeeId,

CONCAT(emp.firstName, ' ', emp.lastName) AS employee,
emp.jobTitle,
mgr.employeeId AS managerId,
CONCAT(mgr.firstName, ' ', mgr.lastName) AS manager

FROM employees emp LEFT JOIN employees mgr
ON emp.managerId = mgr.employeeId;