How To Use Indexes In SQL
In this article, you will learn what indexes are and how to use indexes in SQL.
SQL Indexes are used to find the data immediately in our database. SQL index is same as book index because, in both of these, we use to find the data between several data. If we create an index or delete an index, there is no effect on the data. We only see the work of an index and not the structure of an index in our database.
Indexes are only used in the select queries and where clause. It performs the slow work with an insert and update statement. The index does not allow the redundancy of the data in the column. The index is a unique statement. Index involves the create index statement. In this, we set the name of an index, define the column index and show the data in a series.
The CREATE INDEX:
Create Index command is used to create an index in the table. With the help of an index, we find the data easily in the database. You can create a row store index, before there is data in the table. Use a rowstore index to better the query performance, especially when the queries select from specific columns or require the values to be sorted in a particular order.
The syntax of create index is as follows:
create index index_name on table_name;
- Single-Column Indexes:
With the help of single column index, we create only single column in our table.
The basic syntax for single column index as follows:
create index index_name on table_name (column_name);
- Unique Indexes:
SQL unique index is used to eliminate the duplicate data in the database tables. It helps to remove redundancy of the data; thereby improving the performance.
The basic syntax for the unique index is as follows:
create unique index index_name on table_name (column_name);
- Composite Indexes:
SQL Composite Index is used, when we indexed many columns of a table. If we create any indexed column, one thing is significant. i.e. this data is used many times.
The basic syntax for composite indexes is as follows:
create index index_name on table_name (column1, column2);
- Implicit Indexes:
In SQL, Implicit indexes generates itself in the index, when an object is created in the database. For the primary and unique constraints, indexes are created automatically.
The DROP INDEX :
When we create an index in our table, it is also possible to drop an index. Thus, Drop Index command is used for deleting the index.
The basic syntax for drop index as follows:
drop index index_name;
Thus, we learnt, the indexes are used to find the data immediately and also learn its use in SQL.