Cassandra Group By clause in Select command

1. Go to C:\Program Files\DataStax-DDC\apache-cassandra\conf\cassandra.yaml
change false to true

enable_user_defined_functions: true


2. Paste below functions in cqlsh window

CREATE OR REPLACE FUNCTION state_group_and_count( state map, type text )
CALLED ON NULL INPUT
RETURNS map
LANGUAGE java AS '
Integer count = (Integer) state.get(type);  if (count == null) count = 1; else count++; state.put(type, count); return state; ' ;

CREATE OR REPLACE AGGREGATE group_and_count(text)
SFUNC state_group_and_count
STYPE map 
INITCOND {};


3. execute the query like below

--select group_and_count(column) from table;
-- ex
-- select group_and_count(item) from skutable;



4. you may see like this 
Failed to format value OrderedMapSerializedKey([(u'xxx', 4)]) : 'NoneType' object has no attribute 'sub_types'
this is a cqlsh error. so you can try from programming languages like java..., it may work perfectly.

Add - Remove Column in MongoDB

// add new column and with default value
db.order.update({}, {$set: {"status": 'NEW'}},{multi:true})

//remove a column
db.order.update({}, {$unset: {"status": ''}},{multi:true})

MongoDB - Update statement

//update
db.documentName.update({'_id': ObjectId('566136f3e4b03044bfb8b37e'),'attributeName':'existing-value'},{$set:{'sameAttributeName':'New-value'}})

sample

db.order.update({'_id': ObjectId('566136f3e4b03044bfb8b37e'),'status':'NEW'},{$set:{'status':'COMPLETE'}})







db.login.update({'_id': ObjectId('5667a7ffe4b04ebafe56122e'),'password':'','email':'','mobileNumber':''},{$set:{'password':'qwerty','email':'drvijayy2k2@gmail.com','mobileNumber':'9842088860'}})

MongoDB Install in Linux

1.    Install MongoDB
    Import the public key used by the package management system.

    sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv 7F0CEB10

2. Create a list file for MongoDB.

    echo "deb http://repo.mongodb.org/apt/ubuntu trusty/mongodb-org/3.0 multiverse" | sudo tee /etc/apt/sources.list.d/mongodb-org-3.0.list

3 Reload local package database.

    sudo apt-get update

4 Install the MongoDB packages.

    sudo apt-get install -y mongodb-org

4.1 Install a specific release of MongoDB.

    sudo apt-get install -y mongodb-org=3.0.7 mongodb-org-server=3.0.7 mongodb-org-shell=3.0.7 mongodb-org-mongos=3.0.7 mongodb-org-tools=3.0.7

5. Start MongoDB.

    sudo service mongod start

5.1 Verify that MongoDB has started successfully
    Verify that the mongod process has started successfully by checking the contents of the log file at /var/log/mongodb/mongod.log for a line reading

6 Stop MongoDB.

    sudo service mongod stop

7 Restart MongoDB.
   
    sudo service mongod restart

8. mongodb - uninstall

    sudo service mongod stop
    sudo apt-get purge mongodb-org*
    sudo rm -r /var/log/mongodb
    sudo rm -r /var/lib/mongodb