Why would you allow duplicates in a query?

Why would you allow duplicates in a query?

The query output simply shows you whether the record belongs in the query. If a field with a one-to-many relationship is in your filters, output, or sort, the record will appear multiple times– once for each time the record meets the criteria. This allows you to check your query to ensure you get the expected results.

Why duplicate tables are not allowed in Rdbms?

The main reason could be: Wastage of space for maintaining duplicate records which doesn’t make sense. Unnecessary wastage of memory space (main memory) when you select data in your application. Normalization Constraint: if your table has duplicate records then it’s not a normalized table at all.

Are duplicates allowed in SQL?

Duplicate records in SQL, also known as duplicate rows, are identical rows in an SQL table. This means, for a pair of duplicate records, the values in each column coincide. Generally, duplicate rows are not always allowed in a database or a data table.

Does inner join duplicate?

Yes, if there are duplicate values.

How remove duplicates after join in SQL?

Select column values in a specific order within rows to make rows with duplicate sets of values identical. Then you can use SELECT DISTINCT to remove duplicates. Alternatively, retrieve rows in such a way that near-duplicates are not even selected.

How do you prevent duplicates in SQL joins?

3 Answers

1. ALWAYS put the join predicates in the join.
2. ALSO, sometimes you want to join to the same table more than once, with DIFFERENT predicates for each join.

How do I stop inserting duplicate records in hive?

Remove Duplicate Records from Hive Table

1. Use Insert Overwrite and DISTINCT Keyword.
2. GROUP BY Clause to Remove Duplicate.
3. Use Insert Overwrite with row_number() analytics functions.

Does inner join allow duplicates?