IFB130 Lecture Notes - Lecture 9: Missing Data
19 Oct 2018
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Lecture 9 - sql & relational algebra pt 3. Join / inner join / cross join: natural join, left join, right join, relational algebra: Some picks any value in a specified row i. e some = minimum all others, etc. ) i. e. all = maximum. Aliases: an alias provides a quicker way to reference a table in an sql statement, very useful when constructing statements including one or more join operations, a simple select statement using an alias would be as follows: Joins are used to retrieve related data that is stored across multiple relations: types of joins: Join / inner join / cross join: combines records from two tables, all three of these terms are equivalent. Joining condition defined using the on clause to specify how the two tables should be joined: example: list each student"s name and result for each unit they have a result for:
