Oracle database index advantages and disadvantages description-learning notes

Index category:

Indexes can be divided into clustered indexes, non-clustered indexes, and unique indexes.

Advantages:

1. The main advantage is convenient query and improved system performance.

2. By creating a unique index, You can ensure the uniqueness of each row of data in the database table.

3. The data retrieval speed can be greatly accelerated, which is also the main reason for creating an index.

4. It can accelerate the connection between tables, especially for Data Reference integrity.

5. When you use grouping and sorting clauses to retrieve data, you can also significantly reduce the time for grouping and sorting in queries.

6. By using indexes, you can use the optimizer during the query process to improve system performance.

Someone may ask:

There are so many advantages to adding indexes. Why not create an index for each column in the table?

Disadvantages:

1. It takes time to create and maintain indexes. This time increases with the increase of data volume.

2. Indexes occupy physical space. In addition to data tables, each index occupies a certain amount of physical space,

If you want to create a clustered index, you need more space.

3. When adding, deleting, and modifying table data, the index must also be dynamically maintained,

This reduces the Data Maintenance speed.

4. the query needs to be re-sorted to reduce the efficiency.

5. The indexing efficiency of physical Oracle databases is low. Only one index can be created.

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