Table variables¶

Table variables store data in tabular form. In NebulaGraph Database Developer Edition, they are mainly used to store query results, intermediate traversal results, and to drive batch insertion, update, or deletion of nodes and edges.

The sections below cover local table variables in NebulaGraph Database Developer Edition.

Syntax¶

diagramsource

table_variable_definition
table_value_constructor
table_expression

table_variable_definition ::=
    'BINDING'? 'TABLE' table_variable ( 
        ((( '::' | 'TYPED' ) 'BINDING TABLE')?  
            '{' (field_name value_type) (',' (field_name value_type))* '}' ('=' table_value_constructor)?
        )  
        | '{' field_name (',' field_name)* '}' '=' table_value_constructor
        | '=' table_value_constructor
    ) 

table_value_constructor ::=
    table_expression
    | '{' procedure_body '}' 

table_expression ::=
    ( '{' (field_name ':' value_expression) (',' (field_name ':' value_expression))* '}' ) (',' ( '{' (field_name ':' value_expression) (',' (field_name ':' value_expression))* '}' ) )* 
    | ( '(' value_expression (',' value_expression)* ')' ) ( ',' ( '(' value_expression (',' value_expression)* ')' ) )*

Parameters¶

`table_variable`¶

The name of the table variable to be defined. table_variable can be a regular identifier or a delimited identifier enclosed with backticks (`). For more information about identifiers, see Rules for naming identifiers.

`field_name`¶

The name of a field in the table. field_name must be an identifier. For more information about identifiers, see Rules for naming identifiers.

`value_type`¶

The data type of the value that the field holds. Supported data types include numeric, string, boolean, temporal, vector, list, set, map, and record. For more information, see Data types.

`value_expression`¶

The value of the field in the table. value_expression must be an expression that does not depend on any variables. For more information about value expressions, see Value expressions.

`procedure_body`¶

One or a set of DQL statements to be executed. For more information, see Procedure body and DQL statements.

Member functions¶

clear()¶

Removes all data from the table variable.

Function signature¶

clear() -> VOID

Usage notes¶

You can call clear() only through the SET statement. For more information, see SET statement.

Examples¶

The following examples are based on the example dataset.

Define a table variable without assigning values¶

'''
TABLE t :: TABLE { a INT, 
                   b BOOL, 
                   c TYPED STRING, 
                   d DOUBLE, 
                   e LIST<DECIMAL(10, 4)>, 
                   f RECORD {x INT, y STRING}, 
                   g DATE, 
                   h VECTOR<3,FLOAT> 
   }  
   FINISH
'''

Define a table variable with typed fields¶

'''
TABLE t TYPED TABLE { id INT64, name STRING, birthDate DATE } =  
    { id: 10001, name: 'Alice', birthDate: DATE '1990-01-01' },  
    { id: 10002, name: 'Bob', birthDate: DATE '1991-02-02' },  
    { id: 10003, name: 'Charlie', birthDate: DATE '1992-03-03' }  
FOR re IN t  
RETURN  re.id, re.name, re.birthDate 
'''

The preceding statement defines a table variable t with fields id, name, and birthDate, explicitly specifies the data type of each field, and adds three rows of data to the table. The FOR clause iterates over the table variable t and returns the values of the fields id, name, and birthDate.

Return:

+-------+---------+--------------+
| re.id | re.name | re.birthDate |
+-------+---------+--------------+
| 10001 | Alice   | 1990-01-01   |
| 10002 | Bob     | 1991-02-02   |
| 10003 | Charlie | 1992-03-03   |
+-------+---------+--------------+

Define a table variable with untyped fields¶

'''
TABLE t { id, name, birthDate } =  
    ( 10001, 'Alice', DATE '1990-01-01' ),  
    ( 10002, 'Bob', DATE '1991-02-02' ),  
    ( 10003, 'Charlie', DATE '1992-03-03' )  
FOR re IN t  
RETURN  re.id, re.name, re.birthDate 
'''

The preceding statement defines a table variable t with fields id, name, and birthDate, and specifies the data type of each field implicitly when adding three rows of data to the table. The FOR clause iterates over the table variable t and returns the values of the fields id, name, and birthDate.

Return:

+-------+---------+--------------+
| re.id | re.name | re.birthDate |
+-------+---------+--------------+
| 10001 | Alice   | 1990-01-01   |
| 10002 | Bob     | 1991-02-02   |
| 10003 | Charlie | 1992-03-03   |
+-------+---------+--------------+

Define a table variable from a query result¶

Infer field names and types from the query¶

'''
TABLE t = { USE movie 
            MATCH (v:Person) 
            RETURN v.name AS name, v.id AS id 
            ORDER BY name 
            LIMIT 3 
          } 
FOR rec IN t                                
RETURN rec.name, rec.id
'''

Return:

+------------------+--------+
| rec.name         | rec.id |
+------------------+--------+
| Aaron Eckhart    | 6383   |
| Ada Lonati       | 162562 |
| Adam Alexi-Malle | 20804  |
+------------------+--------+

The preceding statement defines a table variable t from the result of a MATCH statement. The field names (name, id) and their types are inferred from the RETURN clause aliases.

Specify explicit field names¶

'''
TABLE t { personName, personId } = {
    USE movie
    MATCH (v:Person)
    RETURN v.name, v.id
    ORDER BY v.name
    LIMIT 3
}
FOR rec IN t
RETURN rec.personName, rec.personId
'''

Return:

+------------------+--------------+
| rec.personName   | rec.personId |
+------------------+--------------+
| Aaron Eckhart    | 6383         |
| Ada Lonati       | 162562       |
| Adam Alexi-Malle | 20804        |
+------------------+--------------+

The preceding statement defines a table variable t with explicit field names personName and personId. The query returns v.name and v.id, which are mapped to the specified field names in order.

Specify explicit field names and types¶

'''
TABLE t TYPED TABLE { name STRING, id INT64 } = {
    USE movie
    MATCH (v:Person)
    RETURN v.name, v.id 
    ORDER BY v.name
    LIMIT 3
}
FOR rec IN t
RETURN rec.name, rec.id
'''

Return:

+------------------+--------+
| rec.name         | rec.id |
+------------------+--------+
| Aaron Eckhart    | 6383   |
| Ada Lonati       | 162562 |
| Adam Alexi-Malle | 20804  |
+------------------+--------+

The preceding statement defines a table variable t with types. The query output must be compatible with the declared types; otherwise, an error is raised.

Use correlated variables in a query¶

'''
VALUE personId = 100
TABLE friends = {
    USE movie
    MATCH (f:Person)-[:Act]->(m:Movie)
    WHERE f.id = personId
    RETURN f.id AS fid, f.name AS fname
}
FOR rec IN friends
RETURN rec.fid, rec.fname
'''

Return:

+---------+----------------+
| rec.fid | rec.fname      |
+---------+----------------+
| 100     | Scott Speedman |
+---------+----------------+

Remove data from a table variable¶

'''
TABLE t {id, name} = (10, "new1"), (20, "new2")
SET t.clear()
FOR rec IN t
RETURN rec.id, rec.name
'''

Return:

+--------+----------+
| rec.id | rec.name |
+--------+----------+
+--------+----------+

Batch insert nodes with a table variable¶

'''
TABLE t { id, name, birthDate } =  
    ( 10001, 'Alice', DATE '1990-01-01' ),  
    ( 10002, 'Bob', DATE '1991-02-02' ),  
    ( 10003, 'Charlie', DATE '1992-03-03' )  
USE movie 
FOR re IN t 
INSERT (@Actor {id: re.id, name: re.name, birthDate: re.birthDate})
'''

The preceding statement defines a table variable t and iterates over the table variable to insert data into the graph movie as nodes of the node type Actor.

For more information about insert operations, see INSERT.

Batch insert nodes and edges with a table variable¶

'''
TABLE t { actor_id, movie_id, movie_name } =  
    ( 10001 , 20001, 'Movie1' ),  
    ( 10002 , 20002, 'Movie2' ),  
    ( 10003 , 20003, 'Movie3' )  
USE movie 
FOR re IN t 
MATCH (a@Actor) WHERE a.id = re.actor_id 
INSERT (a)-[@Act]->(@Movie {id: re.movie_id, name: re.movie_name})
'''

The preceding statement defines a table variable t and iterates over the table variable to insert data into the graph movie. The statement matches nodes of the node type Actor based on the field actor_id in the table variable and inserts nodes of the node type Movie based on fields movie_id and movie_name in the table variable and also inserts edges between the nodes.

Batch update nodes with a table variable¶

'''
TABLE t { id, new_name } =  
    ( 10001, 'Alice_renamed' ),  
    ( 10002, 'Bob_renamed' ),  
    ( 10003, 'Charlie_renamed' )  
USE movie 
FOR re IN t 
MATCH (a@Actor) WHERE a.id = re.id 
SET a.name = re.new_name
'''

The preceding statement defines a table variable t and matches nodes of the node type Actor based on the field id in the table variable. It then updates the property name of the matched nodes based on the field new_name in the table variable.

For more information about update operations, see SET.

Batch delete nodes with a table variable¶

'''
TABLE t { id } =  
    ( 10001 ),  
    ( 10002 ),  
    ( 10003 )  
USE movie 
FOR re IN t 
MATCH (a@Actor) WHERE a.id = re.id 
DETACH DELETE a
'''

The preceding statement defines a table variable t and matches nodes of the node type Actor based on the field id in the table variable. It then deletes the matched nodes and all their connecting edges.

For more information about delete operations, see DELETE.

Use a table variable in a temporary graph¶

The following example is based on the temporary graph #movie_temporary_graph created in CREATE TEMPORARY GRAPH.

'''
USE #movie_temporary_graph {
    TABLE result_table TYPED TABLE { id INT, name STRING }

    MATCH (a@Movie)
    PER NODE (a) {
        EXPORT a.id AS id, a.name AS name INTO result_table
    }

    FOR r IN result_table
    RETURN r.id AS id, r.name AS name
    LIMIT 3
}
'''

Return:

+-----+------------+
| id  | name       |
+-----+------------+
| 572 | Next Door  |
| 427 | My Uncle   |
| 269 | Breathless |
+-----+------------+

The preceding statement defines a table variable result_table in the existing temporary graph #movie_temporary_graph. The table variable is populated by a match compute statement that exports the id and name fields of Movie nodes into result_table. Finally, the FOR clause iterates over result_table and returns three records.

Table variables¶

Syntax¶

Parameters¶

table_variable¶

field_name¶

value_type¶

value_expression¶

procedure_body¶

Member functions¶

clear()¶

Function signature¶

Usage notes¶

Examples¶

Define a table variable without assigning values¶

Define a table variable with typed fields¶

Define a table variable with untyped fields¶

Define a table variable from a query result¶

Infer field names and types from the query¶

Specify explicit field names¶

Specify explicit field names and types¶

Use correlated variables in a query¶

Remove data from a table variable¶

Batch insert nodes with a table variable¶

Batch insert nodes and edges with a table variable¶

Batch update nodes with a table variable¶

Batch delete nodes with a table variable¶

Use a table variable in a temporary graph¶

`table_variable`¶

`field_name`¶

`value_type`¶

`value_expression`¶

`procedure_body`¶