Includes association - aavedula/how-to-notes GitHub Wiki

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Rails command

  Member.includes(:population)

SQL query

  Member Load (0.5ms)
    SELECT "members".* FROM "members"

  Population Load (0.4ms)
    SELECT "populations".*
    FROM "populations"
    WHERE "populations"."id" IN ($1, $2, $3, $4, $5, $6, $7)
    [["id", "B000NKUUKW"],
     ["id", "B000CDC7O2"],
     ["id", "B0000VG5MG"],
     ["id", "B000A70EOU"],
     ["id", "B000Q71WNG"],
     ["id", "B00067Q8TY"],
     ["id", "B000662QI2"]]

Return value

Loads populations, returns Member records