SQL AND SCALA FOR BEGINNERS: 2 BOOKS IN 1 - Learn Coding Fast! SQL AND SCALA Crash Course, A QuickStart Guide, Tutorial Book by Program Examples, In Easy Steps! by TAM SEL

Author:TAM SEL [SEL, TAM]
Language: eng
Format: azw3
Published: 2019-12-14T00:00:00+00:00

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32) Is it possible to sort a column using a column alias?

Yes. You can use the column alias in the ORDER BY instead of WHERE clause for sorting.

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33) What is the difference between clustered and non-clustered index in SQL?

There are mainly two type of indexes in SQL, Clustered index and non clustered index. The differences between these two indexes is very important from SQL performance perspective.

One table can have only one clustered index, but it can have many non-clustered index. (Approximately 250).

A clustered index determines how data is stored physically in the table. Clustered index stores data in the cluster, related data is stored together, so that retrieval of data becomes simple.

Clustered indexes store the data information and the data itself whereas non-clustered index stores only the information, and then it will refer you to the data stored in clustered data.

Reading from a clustered index is much faster than reading from non-clustered index from the same table.

Clustered index sort and store data row in the table or view based on their key value, while non-cluster has a structure separate from the data row.

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