将限制设置为array_agg（）

select id[1], id[2]from (    SELECt array_agg("Esns".id ) as id    FROM public."Esns",          public."PurchaseOrderItems"     WHERe         "Esns"."PurchaseOrderItemId" = "PurchaseOrderItems".id         AND "PurchaseOrderItems"."GradeId"=2 ) s

或者，如果您希望将输出作为数组，则可以对其进行切片：

SELECt (array_agg("Esns".id ))[1:2] as id_arrayFROM public."Esns",      public."PurchaseOrderItems" WHERe     "Esns"."PurchaseOrderItemId" = "PurchaseOrderItems".id     AND "PurchaseOrderItems"."GradeId"=2