Question

我想选择三列（id_produkt，313,314），所以我尝试了：

create_table "preference_skills", options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
    t.integer "user_id", default: 0
    t.integer "skill_id", default: 0
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
end

 create_table "user_skills", options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
    t.integer "user_id"
    t.integer "skill_id"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
end

create_table "skills", options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
    t.string "name", default: ""
    t.integer "skill_count", default: 0
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
end

但它只返回两列：id_produkt和313。如何获得带有别名的三列？

Answer 1

试试这个SQL代码

select id_produkt, 
case when id_stan_produkt = 313 then 'TAK' 
else 'NIE'
end  as "313",
case when id_stan_produkt = 314 then 'TAK' 
else 'NIE'
end  as "314"
 from bp_stan_produkt where data_do is null

使用CASE WHEN选择两列

1 个答案: