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The following basic-level SQL problems are about ‘Function’. Summarizing values by using SUM, AVG, with IF or conditions

The following basic-level SQL problems are about ‘Function’. e.g. SUM() with IF conditions. LeetCode 1251Average Selling

The following advanced-level SQL problems are about ‘Summary Function’. More: using LEFT to slice the string. LeetCode

The following intro-level SQL problems are about ‘Filtering (HAVING)’. LeetCode 182Duplicate Emails (Easy) [link] Using

The following intro-level SQL problems are about ‘Control Flow’. LeetCode 1158Market Analysis I (Medium) [link] SELECT U

The following intro-level SQL problems are about ‘Function (COUNT, MAX, MIN)’. LeetCode 511Game Play Analysis I (Easy)

The following intro-level SQL problems are about ‘Join (JOIN or WHERE)’. Recall DATEDIFF, WHERE IS. Recall (INNER) JOIN

The following intro-level SQL problems are about manipulating ‘string’ by GROUP_CONCAT, CONCAT, LEFT, RIGHT, SUBSTRING,

The following intro-level SQL problems are about ‘ordering (ORDER BY)’ and ‘editing (CASE WHEN)’. More: DELETE and UPDAT

The following intro-level SQL problems are about ‘combining (UNION) and querying’ and ‘selecting (HAVING)’. More: LIMIT

The following intro-level SQL problems are about ‘selecting (WHERE)’. LeetCode 183Customers Who Never Order (Easy) [link