Delete Vertex command is used to remove vertices from the database. While deleting, it checks and maintains the consistency with the edges and removes all cross-references (with the edges) to the deleted vertex.

The following statement is the basic syntax of Delete Vertex Command.

DELETE VERTEX <vertex> [WHERE <conditions>]
[LIMIT <MaxRecords>>] [BATCH <batch-size>]

Following are the details about the options in the above syntax.

<vertex> − Defines the vertex that you want to remove, using its Class, Record ID, or through a sub-query.

WHERE − Filters condition to determine which records the command removes.

LIMIT − Defines the maximum number of records to be removed.

BATCH − Defines how many records the command removes at a time, allowing you to break large transactions into smaller blocks to save on memory usage.

Example

Try the following command to learn how to delete single vertex or multiple vertices.

Execute the following command to remove the vertex ‘#14:1’.

orientdb> DELETE VERTEX #14:1

If the above command is executed successfully, you will get the following output.

Delete record(s) ''1'' in 0.005000 sec(s)

Execute the following command to remove all vertices from the class ‘Customer’ marked with the property ‘isSpam’.

orientdb> DELETE VERTEX Customer WHERE isSpam = TRUE

If the above command is executed successfully, you will get the following output.

Delete record(s) ''3'' in 0.005000 sec(s)

Alter Property is a command used to modify or update the Property of a particular class. Altering the property means modifying the fields of a table. In this chapter, you can learn how to update the property.

The following statement is the basic syntax of Alter Property Command.

ALTER PROPERTY <class>.<property> <attribute-name> <attribute-value>

Following are the details about the options in the above syntax.

<class> − Defines the class to which the property belongs.

<property> − Defines the property you want to update.

<attribute-name> − Defines the attribute of a property you want to update.

<attribute-value> − Defines the value you want to set on the attribute.

The following table defines the list of attributes to alter the property.

Note − if you are altering NAME or TYPE, this command will take some time to update depending on the amount of data.

Example

Try some queries which are given below to understand Alter property.

Execute the following query to change the name of the property from ‘age’ to ‘born’ in the class Customer.

orinetdb {db = demo}> ALTER PROPERTY Customer.age NAME born

If the above query is executed successfully, you will get the following output.

Property altered successfully

Execute the following query to make ‘name’ as the mandatory property of the class ‘Customer’.

orientdb {db = demo}> ALTER PROPERTY Customer.name MANDATORY TRUE

If the above query is executed successfully, you will get the following output.

Property altered successfully

Cluster is an important concept in OrientDB which is used to store records, documents, or vertices. In simple words, cluster is a place where a group of records are stored. By default, OrientDB will create one cluster per class. All the records of a class are stored in the same cluster, which has the same name as the class. You can create up to 32,767(2^15-1) clusters in a database.

The CREATE class is a command used to create a cluster with a specific name. Once the cluster is created, you can use the cluster to save records by specifying the name during the creation of any data model. If you want to add a new cluster to a class, use Alter Class command and ADDCLUSTER command.

The following statement is the basic syntax of Create Cluster command.

CREATE CLUSTER <cluster> [ID <cluster-id>]

Where <cluster> defines the name of the cluster you want to create and <cluster-id> defines the numeric ID you want to use for the cluster.

The following table provides the list of Cluster selection strategies.

Example

Let us take an example to create a cluster named sales.

orientdb> CREATE CLUSTER sales

If the above query is executed successfully, you will get the following output.

Cluster created correctly with id #12

The Truncate Cluster command deletes all records of a cluster.

The following statement is the basic syntax of Truncate Cluster Command.

TRUNCATE CLUSTER <cluster-name>

Where <cluster-name> is the name of the cluster.

Example

Try the following query to truncate the cluster named sales.

Orientdb {db = demo}> TRUNCATE CLUSTER Profile

If the above query is executed successfully, you will get the following output.

Cluster truncated successfully.

The Drop Cluster command removes the cluster and all its related content. This operation is permanent and rollback.

The following statement is the basic syntax of Drop Cluster command.

DROP CLUSTER <cluster-name>|<cluster-id>

Where <cluster-name> defines the name of the cluster you want to remove and <cluster-id> defines the ID of the cluster you want to remove.

Example

Try the following command to remove Sales cluster.

orientdb> DROP CLUSTER Sales

If the above query is executed successfully, you will get the following output.

Cluster dropped successfully

Alter Cluster command is to update attributes on an existing cluster. In this chapter you can learn how to add or modify the attributes of a cluster.

The following statement is the basic syntax of Alter Cluster command.

ALTER CLUSTER <cluster> <attribute-name> <attribute-value>

Following are the details about the options in the above syntax.

<cluster> − Defines the cluster name.

<attribute-name> − Defines the attribute you want to change.

<attribute-value> − Defines the value you want to set for this attribute.

The following tabular format provides the list of supported attributes you can use along with Alter cluster command.

The following table provides the list of Conflict strategies.

Example

Try the following example queries to learn Alter cluster command.

Execute the following command to change the name of a cluster from Employee to Employee2.

orientdb {db = demo}> ALTER CLUSTER Employee NAME Employee2

If the above command is executed successfully, you will get the following output.

Cluster updated successfully

Execute the following command to change the name of a cluster from Employee2 to Employee using cluster ID.

orientdb {db = demo}> ALTER CLUSTER 12 NAME Employee

If the above command is executed successfully, you will get the following output.

Cluster updated successfully

Execute the following command to change the cluster conflict strategy to automerge.

orientdb {db = demo}> ALTER CLUSTER V CONFICTSTRATEGY automerge

If the above command is executed successfully, you will get the following output.

Cluster updated successfully

Property in OrientDB works like a field of class and column in the database table. Create Property is a command used to create a property for a particular class. The class name that you used in the command must exist.

The following statement is the basic syntax of Create Property command.

CREATE PROPERTY <class-name>.<property-name> <property-type> [<linked-type>][ <linked-class>]

Following are the details about the options in the above syntax.

<class-name> − Defines the class you want to create the property in.

<property-name> − Defines the logical name of the property.

<property-type> − Defines the type of property you want to create.

<linked-type> − Defines the container type, used in container property type.

<linked-class> − Defines the container class, used in container property type.

The following table provides the data type for property so that OrientDB knows the type of data to store.

In addition to these there are several other property types that work as containers.

Example

Try the following example to create a property name on the class Employee, of the String type.

orientdb> CREATE PROPERTY Employee.name STRING

If the above query is executed successfully, you will get the following output.

Property created successfully with id = 1

The Drop Class command removes a class from the schema. It is important to pay attention and maintain a consistent schema. For example, avoid to remove classes that are super-classes of others. The associated cluster won”t be deleted.

The following statement is the basic syntax of Drop Class command.

DROP CLASS <class>

Drop a class with the class name.

Example

Try the following query to Drop a class Employee.

Orientdb> DROP CLASS Employee

If the above query is executed successfully, you will get the following output.

Class dropped successfully

Truncate class will delete all records of clusters defined as part of class. In OrientDB, every class has an associated cluster with the same name. If you want to also remove all records from the class hierarchy, you need to use the POLYMORPHIC keyword.

The following statement is the basic syntax of Truncate Class command.

TRUNCATE CLASS <class> [ POLYMORPHIC ] [ UNSAFE ]

Following are the details about the options in the above syntax.

<class> − Defines the class you want to truncate.

POLYMORPHIC − Defines whether the command also truncates the hierarchy.

UNSAFE − Defines the command forces truncation on vertex or edge class.

Example

The following query to truncate a class Profile.

orientdb> TRUNCATE CLASS Profile

If the above query is executed successfully, you will get the following output.

Class truncated successfully

Class and Property in OrientDB are used to build a schema with the respective attributes such as class name, super-class, cluster, number of clusters, Abstract, etc. If you want to modify or update any attribute of existing classes in the schema then you have to use Alter Class command.

The following statement is the basic syntax of the Alter Class Command.

ALTER CLASS <class> <attribute-name> <attribute-value>

Following are the details about the options in the above syntax.

<class> − Defines the class name.

<attribute-name> − Defines the attribute you want to change.

<attribute-value> − Defines the value you want to set for the attribute.

The following table defines the list of attributes that support Alter Class command.

Example

Let us try few examples that will update or modify the attributes of the existing class.

The following query is used to define a super-class ‘Person’ for an existing class ‘Employee’.

orientdb> ALTER CLASS Employee SUPERCLASS Person

If the above query is executed successfully, you will get the following output.

Class altered successfully

The following query is used to add a super-class ‘Person’ for an existing class ‘Employee’.

orientdb> ALTER CLASS Employee SUPERCLASS +Person

If the above query is executed successfully, you will get the following output.

Class altered successfully