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Alter Table in Cassandra

Cassandra Alter Table
To alter an existing table, the ALTER TABLE command is used. This command can be used to add a column or to Drop a column.
Syntax:

ALTER (TABLE | COLUMN_FAMILY) tablename instruction  

To Add a Column:

The column name should not conflict with the existing column names. The table should not be defined with a compact storage option.

Syntax:

ALTER TABLE table_name  
ADD new column datatype;

Example:
Employees table before alteration:

id	name	salary
1	Adi	50000
2	Bruno	30000
3	Chris	60000
4	Davis	20000
5	Eliza	15000

Query:

ALTER TABLE employees  
ADD city text;

Explanation:
The ’employees’ is an already created table. A new column named ‘city’ is added to the table. Verify it by using the below command.
SELECT * FROM employees;
Output:

id	name	salary	city
1	Adi	50000	
2	Bruno	30000	
3	Chris	60000	
4	Davis	20000	
5	Eliza	15000	

To Drop a Column:

The table should not be defined with a compact storage option.
Syntax:

ALTER table_name  
DROP column_name;   

Example 1:
Employees table before alteration:

id	name	salary	city
1	Adi	50000	Delhi
2	Bruno	30000	London
3	Chris	60000	New York
4	Davis	20000	New York
5	Eliza	15000	London

Query:

ALTER TABLE employees  
DROP city;

Explanation:
The ’employees’ is an already created table. A column named ‘city’ is dropped from the table. All the data of the column is thus also dropped. Verify it by using the below command.
SELECT * FROM employees;
Output:

id	name	salary
1	Adi	50000
2	Bruno	30000
3	Chris	60000
4	Davis	20000
5	Eliza	15000

Example 2:
Employees table before alteration:

id	name	salary
1	Adi	50000
2	Bruno	30000
3	Chris	60000
4	Davis	20000
5	Eliza	15000

Query:

ALTER TABLE employees  
DROP (name, salary);

Explanation:
The ’employees’ is an already created table. Here two columns named ‘name’ and ‘salary’ are dropped from the table. All the data of the columns is thus also dropped. Verify it by using the below command.
SELECT * FROM employees;

Output:

id
1
2
3
4
5
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