Joins

TODO

• Mnemonic: Join vs Joins What does it do? it Joins

Joins

• Join returns only the rows that have matching values in both the tables

User.joins(:posts)

# SELECT "users".*

# FROM "users"

# INNER JOIN "posts" ON "posts"."user_id" = "users"."id"

Multiple joins:

User.joins(:posts, :account)

# SELECT "users".*

# FROM "users"

# INNER JOIN "posts" ON "posts"."user_id" = "users"."id"

# INNER JOIN "accounts" ON "accounts"."id" = "users"."account_id"

LetOuterJoins || left_joins (Alias)

• Returns all the rows from the LEFT table and matching records between both the tables.