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.

• 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.

YIELD clauses¶

Syntax¶

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

Use a YIELD clause in a statement¶

• Use YIELD with GO:

  nebula> GO FROM "player100" OVER follow \
          YIELD $$.player.name AS Friend, $$.player.age AS Age;
  +-----------------+-----+
  | Friend          | Age |
  +-----------------+-----+
  | "Tony Parker"   | 36  |
  +-----------------+-----+
  | "Manu Ginobili" | 41  |
  +-----------------+-----+
  

• Use YIELD with FETCH:

  nebula> FETCH PROP ON player "player100" \
          YIELD player.name;
  +-------------+--------------+
  | VertexID    | player.name  |
  +-------------+--------------+
  | "player100" | "Tim Duncan" |
  +-------------+--------------+
  

• Use YIELD with LOOKUP:

  nebula> LOOKUP ON player WHERE player.name == "Tony Parker" \
          YIELD player.name, player.age;
  =======================================
  | VertexID | player.name | player.age |
  =======================================
  | 101      | Tony Parker | 36         |
  ---------------------------------------
  

YIELD statements¶

Syntax¶

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

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 follow._dst AS ID \
        | FETCH PROP ON player $-.ID \
        YIELD player.age AS Age \
        | YIELD AVG($-.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 follow.degree AS Degree, follow._dst 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      |
+--------+