初学,弱弱地问存储过程最基本知识
比如:
USE pubs
IF EXISTS(SELECT name FROM sysobjects
WHERE name='au_info_all' AND type='P')
DROP PROCEDURE au_info_all
GO
CREATE PROCEDURE au_info_all
AS
SELECT au_lname,au_fname,title,pub_name
FROM authors a INNER JOIN titleauthor ta
ON a.au_id=ta.au_id INNER JOIN titles t
ON t.title_id=ta.title_id INNER JOIN publishers p
ON t.pub_id=p.pub_id
-----------------------
1、IF EXISTS(。。。) DROP 。。。这句什么意思?这里的SELECT 和下面的SELECT有何关系??我看不出有什么关系嘛?!
2、FROM authors a INNER JOIN titleauthor ta这句后面的“a INNER JOIN titleauthor ta”什么意思?
3、ON a.au_id=ta.au_id INNER JOIN titles t这句,“ON a.au_id=ta.au_id ”什么意思?同样地,“INNER JOIN titles t”什么意思?