Create an index (basic conditions. For other constraints, see query ):
Create [index type] Index name on table name (column name)
Advantages:
- First, you can create a unique index to ensure the uniqueness of each row of data in the database table.
- Second, it can greatly speed up data retrieval, which is also the main reason for creating an index.
- Third, it can accelerate the connection between tables, especially in achieving Data Reference integrity.
- Fourth, when you use grouping and sorting clauses to retrieve data, you can also significantly reduce the time for grouping and sorting in queries.
- Fifth, by using indexes, you can use the optimizer during the query process to improve system performance.
Disadvantages:
- First, it takes time to create and maintain indexes. This time increases with the increase of data volume.
- Second, indexes occupy physical space. In addition to data tables, each index occupies a certain amount of physical space. To create a clustered index, the required space is larger.
- Third, when adding, deleting, and modifying data in the table, the index must also be dynamically maintained, which reduces the Data Maintenance speed.
Index creation, advantages and disadvantages
