Friday, 7 February 2020

Cassandra: Delete all the rows from a table

Using ‘TRUNCATE’ command, you can delete all the rows from a table.

Syntax:
<truncate-stmt> ::= TRUNCATE ( TABLE | COLUMNFAMILY )? <tablename>

Example:
TRUNCATE keyspaceName.tableName;

If you are already in the keyspace, then you can use the tableName directly.

TRUNCATE tableName;

cqlsh> CREATE KEYSPACE cassandratutorial WITH REPLICATION = 
   ... { 
   ...   'class' : 'SimpleStrategy', 
   ...   'replication_factor' : 1 
   ... };
cqlsh> 
cqlsh> CREATE TABLE IF NOT EXISTS cassandratutorial.employee (
   ...   id INT PRIMARY KEY, 
   ...   firstName VARCHAR,
   ...   lastName VARCHAR,
   ...   age int
   ... );
cqlsh> 
cqlsh> INSERT INTO cassandratutorial.employee JSON '{"id" : 1, "firstName" : "Krishna", "lastName" : "Gurram", "age" : 30}';
cqlsh> INSERT INTO cassandratutorial.employee JSON '{"id" : 2, "firstName" : "Ram", "lastName" : "Gurram", "age" : 31}' ;
cqlsh> INSERT INTO cassandratutorial.employee JSON '{"id" : 3, "firstName" : "Vijay", "lastName" : "Ponnam", "age" : 45}';
cqlsh> INSERT INTO cassandratutorial.employee JSON '{"id" : 4, "firstName" : "Chitra", "lastName" : "Rajan", "age" : 45}';
cqlsh> 
cqlsh> SELECT * FROM cassandratutorial.employee;

 id | age | firstname | lastname
----+-----+-----------+----------
  1 |  30 |   Krishna |   Gurram
  2 |  31 |       Ram |   Gurram
  4 |  45 |    Chitra |    Rajan
  3 |  45 |     Vijay |   Ponnam

(4 rows)
cqlsh> 
cqlsh> TRUNCATE cassandratutorial.employee;
cqlsh> 
cqlsh> SELECT * FROM cassandratutorial.employee;

 id | age | firstname | lastname
----+-----+-----------+----------

(0 rows)



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