①1.?相同的表的自连接和不同表间的普通连接并没有什么区别,自连接里的"自"这个词也没有太大的意义
?SELECT P1.name AS name_1, P2.name AS name_2
??FROM Products P1, Products P2;
?SELECT P1.name AS name_1, P2.name AS name_2
??FROM Products P1, Products P2
?WHERE P1.name ＜＞ P2.name;
?SELECT P1.name AS name_1, P2.name AS name_2
??FROM Products P1, Products P2
?WHERE P1.name ＞ P2.name;
?SELECT P1.name AS name_1, P2.name AS name_2, P③name AS name_3
??FROM Products P1, Products P2, Products P3
?WHERE P1.name ＞ P2.name
??AND P2.name ＞ P③name;
?DELETE FROM Products P1
?WHERE rowid ＜ ( SELECT MAX(P2.rowid)
????FROM Products P2
????WHERE P1.name = P2. name
?????AND P1.price = P2.price ) ;
?DELETE FROM Products P1
?WHERE EXISTS ( SELECT ＊
????FROM Products P2
????WHERE P1.name = P2.name
????AND P1.price = P2.price
????AND P1.rowid ＜ P2.rowid );
?SELECT DISTINCT A1.name, A1.address
??FROM Addresses A1, Addresses A2
?WHERE A1.family_id = A2.family_id
??AND A1.address ＜＞ A2.address ;
?SELECT DISTINCT P1.name, P1.price
??FROM Products P1, Products P2
?WHERE P1.price = P2.price
??AND P1.name ＜＞ P2.name;
?SELECT name, price,
??RANK() OVER (ORDER BY price DESC) AS rank_1,
??DENSE_RANK() OVER (ORDER BY price DESC) AS rank_2
??FROM Products;
?SELECT P1.name,
??P1.price,
??(SELECT COUNT(P2.price)
???FROM Products P2
???WHERE P2.price ＞ P1.price) + 1 AS rank_1
??FROM Products P1
??ORDER BY rank_1;
?SELECT P1.name,
??MAX(P1.price) AS price,
??COUNT(P2.name) +1 AS rank_1
??FROM Products P1 LEFT OUTER JOIN Products P2
??ON P1.price ＜ P2.price
?GROUP BY P1.name
?ORDER BY rank_1;
?SELECT P1.name,
??MAX(P1.price) AS price,
??COUNT(P2.name) +1 AS rank_1
??FROM Products P1 INNER JOIN Products P2
??ON P1.price ＜ P2.price
?GROUP BY P1.name
?ORDER BY rank_1;
?SELECT P1.name, P2.name
??FROM Products P1 LEFT OUTER JOIN Products P2
??ON P1.price ＜ P2.price;
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