Create index syntax on MongoDB
Create index on employees table with column employee_id in ascending order.
--Create index on employees table with column employee_id in ascending order
db.employees.ensureIndex( { emp_id: 1 } )
Create index on employees table with column emp_id and age(desc order)
db.employees.ensureIndex( { emp_id: 1, age: -1 } )
Example of SQL query for RDBMS database e.g Oracle, SQL Server
-- Create index in SQL query with one column ascending order.
create index on idx_emp on employees (emp_id);
--Create index in SQL query with ascending or descending order.
create index on idx_emp1 on employees(emp_id,age desc);
Drop index in MongoDB
db.collection.dropIndex(index)
-- Example drop index employee_id_idx on employees table.
db.employees.dropIndex("emp_id_idx")
-- Drop index with column name specification as created first index in this blog.
db.pets.dropIndex( { "emp_id" :1 } )
Get the list of index present on collection/table
db.collection.getIndexes()
Example:
-- Get list of indexes present on employees table
db.employees.getIndexes()
