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Unit 5 Database Discussion Assignment

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Unit 5 database discussion assignment Assuming we are joining on columns with no duplicates, which is a very common case: An inner join of X and Y gives the result of y intersect z, i.e. the inner part of y intersection. An outer join of y and z gives the results of A union z, i.e. the outer parts of y Venn diagram union. Simple Examples if we have two tables, which contains a single column each, with the data as follows: y z - - 1 3 2 4 3 5 4 6 in the above given data lists table case for example (1,2) are unique to y, (3,4) are common, and (5,6) are unique to z. Inner join An inner join using either of the equivalent queries gives the intersection of the two tables, i.e. the two rows they have in common. select * from a INNER JOIN b on y.y = z.z; …show more content…

select * from a LEFT OUTER JOIN b on y.y = z.z; select y.*,z.* from y,z where y.y = z.z(+); y | z --+----- 1 | null 2 | null 3 | 3 4 | 4 Right outer join A right outer join will give all rows in z, plus any common rows in y. select * from a RIGHT OUTER JOIN b on y.y = z.z; select y.*,z.* from y,z where y.y(+) = z.z; y | z -----+---- 3 | 3 4 | 4 null | 5 null | 6 Full outer join A full outer join will give you the union of y and z, i.e. all the rows in A and all the rows in z. If something in y doesn't have a corresponding datum in z, then the z portion is null, and vice versa. select * from a FULL OUTER JOIN b on Y.Y = Z.Z; y | z -----+----- 1 | null 2 |

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