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Leetcode SQL: 1581. Customer Who Visited but Did Not Make Any Transactions
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1581. Customer Who Visited but Did Not Make Any Transactions SQL Code: SELECT customer_id, COUNT(*) FROM Visits v WITH (NOLOCK) LEFT JOIN Transactions t WITH (NOLOCK) ON v.visit_id = t.visit_id WHERE t.transaction_id IS NULL GROUP BY customer_id; Explanation: *SELECT customer_id, COUNT()**: This line specifies that we want to retrieve the…
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Leetcode SQL: 378. Replace Employee ID With The Unique Identifier
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378. Replace Employee ID With The Unique Identifier SQL Code: SELECT eu.unique_id, [name] FROM Employees e WITH (NOLOCK) LEFT OUTER JOIN EmployeeUNI eu WITH (NOLOCK) ON e.id = eu.id; Explanation: SELECT eu.unique_id, [name]: This line specifies that we want to retrieve the unique_id from the EmployeeUNI table and the name…
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Leetcode SQL: 1683. Invalid Tweets
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1683. Invalid Tweets SQL Code: SELECT tweet_id FROM Tweets WITH (NOLOCK) WHERE LEN(content) > 15; Explanation: SELECT tweet_id: This line specifies that we want to retrieve the tweet_id column from the Tweets table. The tweet_id represents the unique identifier for each tweet. 这一行指定了我们要从 Tweets 表中获取 tweet_id 列，tweet_id 是每条推文的唯一标识符。 FROM Tweets…
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Leetcode SQL: 1148. Article Views
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1148. Article Views I Corrected SQL Code: SELECT DISTINCT [author_id] AS id FROM Views WITH (NOLOCK) WHERE author_id = viewer_id ORDER BY [author_id]; Explanation: SELECT DISTINCT [author_id] AS id: We are selecting the author_id column from the Views table, but we are using the DISTINCT keyword to ensure that only…
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Leetcode SQL: 595: Big Countries
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595. Big Countries SQL Code: SELECT [name], [population], [area] FROM World (NOLOCK) WHERE area >= 3000000 OR population >=25000000 Explanation: SELECT name, population, area: This line specifies that we want to retrieve three columns: name, population, and area from the World table. name: Represents the name of the country. population:…
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Leetcode SQL: 584. Find Customer Referee
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584. Find Customer Referee Corrected SQL Code: SELECT name FROM Customer WHERE referee_id IS NULL OR referee_id != 2; Explanation: SELECT name: This specifies that we want to retrieve the name column from the Customers table, which holds the names of the customers. 这一行指定了我们要从 Customers 表中获取 name 列，name 表示客户的名字。 FROM…
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Leetcode SQL: 1757. Recyclable and Low Fat Products
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1757. Recyclable and Low Fat Products Improved SQL Code: SELECT product_id FROM Products WITH (NOLOCK) WHERE low_fats = 'Y' AND recyclable = 'Y' AND product_id IS NOT NULL; Explanation: SELECT product_id: We are selecting the product_id column from the Products table. This column contains the unique identifiers for each product.…
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LeetCode: 2 Add Two Numbers
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You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order, and each of their nodes contains a single digit. Add the two numbers and return the sum as a linked list. You may assume the two numbers do not contain any leading…
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LeetCode: 543 Diameter of Binary Tree
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Given the root of a binary tree, the diameter of the tree is the length of the longest path between any two nodes in the tree. This path may or may not pass through the root. The length of a path between two nodes is represented by the number of…
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LeetCode: 88 Merge Sorted Array
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You are given two integer arrays nums1 and nums2, sorted in non-decreasing order, and two integers m and n, representing the number of elements in nums1 and nums2, respectively. You need to merge nums2 into nums1 as one sorted array. The final sorted array should not be returned by the…