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YIELD

YIELD defines the output of an nGQL query.

YIELD can lead a clause or a statement:

  • A YIELD clause works in nGQL statements such as GO, FETCH, or LOOKUP and must be defined to return the result.
  • A YIELD statement works in a composite query or independently.

OpenCypher compatibility

This topic applies to native nGQL only. For the openCypher syntax, use RETURN.

YIELD has different functions in openCypher and nGQL.

  • In openCypher, YIELD is used in the CALL[…YIELD] clause to specify the output of the procedure call.

    Note

    NGQL does not support CALL[…YIELD] yet.

  • In nGQL, YIELD works like RETURN in openCypher.

Note

In the following examples, $$ and $- are reference operators. For more information, see Operators.

YIELD clauses

Syntax

YIELD [DISTINCT] <col> [AS <alias>] [, <col> [AS <alias>] ...];
Parameter Description
DISTINCT Aggregates the output and makes the statement return a distinct result set.
col A field to be returned. If no alias is set, col will be a column name in the output.
alias An alias for col. It is set after the keyword AS and will be a column name in the output.

Use a YIELD clause in a statement

  • Use YIELD with GO:
    nebula> GO FROM "player100" OVER follow \
        YIELD properties($$).name AS Friend, properties($$).age AS Age;
+-----------------+-----+
| Friend          | Age |
+-----------------+-----+
| "Tony Parker"   | 36  |
| "Manu Ginobili" | 41  |
+-----------------+-----+
  • Use YIELD with FETCH:
    nebula> FETCH PROP ON player "player100" \
        YIELD properties(vertex).name;
+-------------------------+
| properties(VERTEX).name |
+-------------------------+
| "Tim Duncan"            |
+-------------------------+
  • Use YIELD with LOOKUP:
    nebula> LOOKUP ON player WHERE player.name == "Tony Parker" \
        YIELD properties(vertex).name, properties(vertex).age;
+-------------------------+------------------------+
| properties(VERTEX).name | properties(VERTEX).age |
+-------------------------+------------------------+
| "Tony Parker"           | 36                     |
+-------------------------+------------------------+

YIELD statements

Syntax

YIELD [DISTINCT] <col> [AS <alias>] [, <col> [AS <alias>] ...]
[WHERE <conditions>];

| Parameter | Description | |--------------+---------------------------------------------------------------------------------------------------------| | DISTINCT | Aggregates the output and makes the statement return a distinct result set. | | col | A field to be returned. If no alias is set, col will be a column name in the output. | | alias | An alias for col. It is set after the keyword AS and will be a column name in the output. | | conditions | Conditions set in a WHERE clause to filter the output. For more information, see WHERE. |

Use a YIELD statement in a composite query

In a composite query, a YIELD statement accepts, filters, and modifies the result set of the preceding statement, and then outputs it.

The following query finds the players that "player100" follows and calculates their average age.

nebula> GO FROM "player100" OVER follow \
        YIELD dst(edge) AS ID \
        | FETCH PROP ON player $-.ID \
        YIELD properties(vertex).age AS Age \
        | YIELD AVG($-.Age) as Avg_age, count(*)as Num_friends;
+---------+-------------+
| Avg_age | Num_friends |
+---------+-------------+
| 38.5    | 2           |
+---------+-------------+

The following query finds the players that "player101" follows with the follow degrees greater than 90.

nebula> $var1 = GO FROM "player101" OVER follow \
        YIELD properties(edge).degree AS Degree, dst(edge) as ID; \
        YIELD $var1.ID AS ID WHERE $var1.Degree > 90;
+-------------+
| ID          |
+-------------+
| "player100" |
| "player125" |
+-------------+

Use a standalone YIELD statement

A YIELD statement can calculate a valid expression and output the result.

nebula> YIELD rand32(1, 6);
+-------------+
| rand32(1,6) |
+-------------+
| 3           |
+-------------+

nebula> YIELD "Hel" + "\tlo" AS string1, ", World!" AS string2;
+-------------+------------+
| string1     | string2    |
+-------------+------------+
| "Hel    lo" | ", World!" |
+-------------+------------+

nebula> YIELD hash("Tim") % 100;
+-----------------+
| (hash(Tim)%100) |
+-----------------+
| 42              |
+-----------------+

nebula> YIELD \
      CASE 2+3 \
      WHEN 4 THEN 0 \
      WHEN 5 THEN 1 \
      ELSE -1 \
      END \
      AS result;
+--------+
| result |
+--------+
| 1      |
+--------+
Last update: January 14, 2022
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