视图，函数，存储过程

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视图

创建一个视图 player_above_avg_height

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CREATE VIEW player_above_avg_height AS
SELECT player_id, height
FROM player
WHERE height > (SELECT AVG(height) from player)

实际效果

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SELECT * FROM player_above_avg_height

# 相当于

SELECT player_id, height
FROM player
WHERE height > (SELECT AVG(height) from player)

函数

存储过程

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CREATE PROCEDURE `add_num`(IN n INT)
BEGIN
       DECLARE i INT;
       DECLARE sum INT;
       
       SET i = 1;
       SET sum = 0;
       WHILE i <= n DO
              SET sum = sum + i;
              SET i = i +1;
       END WHILE;
       SELECT sum;
END