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Write a SQL query to get the second highest salary from the Employee table. For example, given the above Employee table, the query should return 200 a 阅读全文
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Write a SQL query to delete all duplicate email entries in a table named Person, keeping only unique emails based on its smallest Id. For example, aft 阅读全文
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There is a table courses with columns: student and class Please list out all classes which have more than or equal to 5 students. For example, the tab 阅读全文
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Given a Weather table, write a SQL query to find all dates' Ids with higher temperature compared to its previous (yesterday's) dates. + + + + | Id(INT 阅读全文
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Suppose that a website contains two tables, the Customers table and the Orders table. Write a SQL query to find all customers who never order anything 阅读全文