LEFT JOIN与RIGHT JOIN学习笔记

--82
SELECT COUNT(*) FROM [tbiz_PuzzleBasic]

SELECT A.BasicID,A.Name,A.Gender,B.WorkID,B.Company,B.Position
FROM [tbiz_PuzzleBasic] A LEFT JOIN [tbiz_PuzzleWork] B ON B.BasicID = A.BasicID

读作:A表在B表的左边,A表的中的记录都将返回,A表是主表

FROM [tbiz_PuzzleBasic] A RIGHT JOIN [tbiz_PuzzleWork] B ON B.BasicID = A.BasicID
--读作A表在B表的右边,这时B表作为主表

小结:始终看两表在"现实"中按从左到右出现的先后顺序来决定"谁"是主表,