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Linear query statement

The linear query statement consists of a linear composition of simple query statements, which are executed sequentially to produce a single result set.

Syntax

linear_query_statement
use_graph_clause simple_query_statement use_graph_clause simple_query_statement primitive_result_statement use_graph_clause primitive_result_statement simple_query_statement primitive_result_statement use_graph_clause { procedure_body }
simple_query_statement
match_statement let_statement for_statement filter_statement paging_statement call_procedure_statement 

linear_query_statement ::=
    ((use_graph_clause simple_query_statement+)+)? use_graph_clause simple_query_statement+ primitive_result_statement
  | use_graph_clause primitive_result_statement
  | ( simple_query_statement+)? primitive_result_statement
  | use_graph_clause? '{' procedure_body '}'

simple_query_statement ::=
   match_statement 
  | let_statement 
  | for_statement 
  | filter_statement 
  | paging_statement  
  | call_procedure_statement

Parameters

use_graph_clause

Declares the working graph of the query. This clause is required only if the query involves a graph and no home graph is set in the current session. For how to set the home graph, see SESSION SET.

For more information about the clause, see USE clause.

simple_query_statement

Performs a simple query. A simple query statement can be one of the following:

  • match_statement
  • let_statement
  • for_statement
  • filter_statement
  • paging_statement
  • call_procedure_statement

match_statement

Retrieves data from the working graph by pattern matching. For more information, see MATCH.

let_statement

Declares variables that can be used in subsequent statements. For more information, see LET.

for_statement

Iterates over a list of elements. For more information, see FOR.

filter_statement

Selects a subset of the results produced by the preceding statement. For more information, see FILTER.

paging_statement

Divides a set of results into discrete subsets or pages. For more information, see Paging.

call_procedure_statement

Calls a procedure. For more information, see Call inline procedures and Call named procedures.

primitive_result_statement

Returns the result of the query. For more information, see Primitive result.

procedure_body

The body of a procedure. It cannot contain any DML or DDL statements. For more information, see Procedure body.

Examples

The following examples are based on the example dataset.

Perform a linear query with the USE clause

'''
USE movie 
MATCH (v@`User`{id: 123})-[e:Watch]->(m:Movie) 
FILTER WHERE e.rate > 3 
RETURN m.name AS movie, e.rate AS rate 
ORDER BY rate DESC 
'''

The preceding statement retrieves the movies watched by the person with an ID of 123 and filters the movies with a rating greater than 3. It then returns the movie names and their ratings in descending order.

Return:

+-----------------------+------+
| movie                 | rate |
+-----------------------+------+
| Star Wars             | 4.0  |
| Star Wars: A New Hope | 4.0  |
| City of God           | 3.5  |
+-----------------------+------+

Perform a linear query without the USE clause

'''
LET nums = LIST[1, 2, 3, 4, 5]
FOR i IN nums
FILTER i % 2 = 1
RETURN i AS odd
ORDER BY odd DESC
'''

Return:

+-----+
| odd |
+-----+
| 5   |
| 3   |
| 1   |
+-----+

Chain two linear segments with NEXT

'''
FOR i IN RANGE(1, 8)
RETURN i AS num
NEXT
FILTER num >= 5
RETURN num
ORDER BY num
'''

Return:

+-----+
| num |
+-----+
| 5   |
| 6   |
| 7   |
| 8   |
+-----+