mirror of https://github.com/dunwu/db-tutorial.git
49 lines
1.2 KiB
SQL
49 lines
1.2 KiB
SQL
-- 第N高的薪水
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--
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-- 编写一个 SQL 查询，获取 Employee 表中第 n 高的薪水（Salary）。
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--
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-- +----+--------+
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-- | Id | Salary |
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-- +----+--------+
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-- | 1 | 100 |
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-- | 2 | 200 |
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-- | 3 | 300 |
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-- +----+--------+
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-- 例如上述 Employee 表，n = 2 时，应返回第二高的薪水 200。如果不存在第 n 高的薪水，那么查询应返回 null。
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--
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-- +------------------------+
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-- | getNthHighestSalary(2) |
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-- +------------------------+
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-- | 200 |
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-- +------------------------+
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USE db_tutorial;
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CREATE TABLE IF NOT EXISTS employee (
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id INT PRIMARY KEY AUTO_INCREMENT,
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salary INT
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);
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INSERT INTO employee(salary)
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VALUES (100);
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INSERT INTO employee(salary)
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VALUES (200);
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INSERT INTO employee(salary)
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VALUES (300);
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SELECT DISTINCT salary
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FROM employee e
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WHERE 1 = (SELECT COUNT(DISTINCT salary)
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FROM employee
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WHERE salary >= e.salary);
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CREATE FUNCTION getNthHighestSalary(n INT) RETURNS INT
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BEGIN
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RETURN (
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SELECT DISTINCT salary
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FROM employee e
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WHERE n = (SELECT COUNT(DISTINCT salary)
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FROM employee
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WHERE salary >= e.salary)
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);
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END
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