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2answers
42 views

How are derived table implemented in MySQL

When MySQL makes a derived table as a result of SELECT (SELECT ...) etc or SELECT * FROM a JOIN (SELECT * from B) etc or SELECT * FROM (SELECT ...) Are these derived temporary tables created ...
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0answers
56 views

Union within derived table, (related_id=a AND related_id=b) OR (related_id=z)

I have the following tables: users, tags, tags_data. tags_data contains tag_id and user_id columns to link the users with tags in a 1 user to many tags relationship. What is the best way of listing ...
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2answers
2k views

Are there advantages to using temporary tables over derived tables in SQL Server?

I read the derived tables have better performance than temporary tables, but anyway many SQL Server developers prefer the second ones. Why? I must do queries with large data (millions records) and I ...