MySql同一张表上的多个连接-获取多个账本/钱包的期末余额

事务

表架构：

--------------------------------------
| user_id | currency | amount | date |
--------------------------------------
|       1 |      eur |    500 | ...  |
|       1 |      gbp |    100 | ...  |
|       1 |      usd |     10 | ...  |
|       1 |      usd |     10 | ...  |
|       1 |      gbp |    100 | ...  |
|       1 |      usd |     10 | ...  |
|       1 |      usd |     10 | ...  |
|       2 |      jpy |     99 | ...  |
|       1 |      jpy |     99 | ...  |
--------------------------------------

我想要的是：

-----------------------------------
|         | total balances        |
| user_id | eur | usd | gbp | jpy |
-----------------------------------
|       1 | 500 |  40 | 200 |  99 |
|       2 |   0 |   0 |   0 |  99 |
-----------------------------------

我的查询代码（使用Laravel的雄辩ORM）：

结果SQL:

select 
      SUM(t1.amount) AS total_eur,
      SUM(t2.amount) AS total_gbp,
      SUM(t3.amount) AS total_usd,
      SUM(t4.amount) AS total_jpy,
      u.id AS u_id,
      u.username AS u_username
      
   from `users` as `u` 
   left join `transactions` as `t1` on `t1`.`user_id` = `u`.`id`
   left join `transactions` as `t2` on `t2`.`user_id` = `u`.`id`
   left join `transactions` as `t3` on `t3`.`user_id` = `u`.`id` 
   left join `transactions` as `t4` on `t4`.`user_id` = `u`.`id` 
   
   where `t1`.`wallet_type` = 'eur'
     and `t2`.`wallet_type` = 'gbp'
     and `t3`.`wallet_type` = 'usd'
     and `t3`.`wallet_type` = 'jpy'

   group by `u`.`id`

当使用3个或更多联接时（

transactions

table只有~600行），速度非常慢
当我只使用两种货币/只使用两种连接时，速度相当快（不到1秒）

我认为多次加入同一个表是一种糟糕的做法。

---

有什么方法可以优化查询吗？

您需要

$query = DB::table('users AS u')
    ->join ('transactions AS t1', 't1.user_id', '=', 'u.id')
    ->selectRaw('
        u.id AS u_id,
        u.username AS u_username,
        SUM(CASE WHEN t1.currency = \'eur\' THEN t1.amount END) AS total_eur,
        SUM(CASE WHEN t1.currency = \'usd\' THEN t1.amount END) AS total_usd,
        SUM(CASE WHEN t1.currency = \'gbp\' THEN t1.amount END) AS total_gbp,
        SUM(CASE WHEN t1.currency = \'jpy\' THEN t1.amount END) AS total_jpy
    ')
    ->groupBy('u.id');

检查语法-我不使用Laravel

---

如果某些货币未列在某些用户数据中，您将得到NULL。如果需要零，则将表达式扩展到t1.currency=\'xxx\'时的

情况，然后t1.amount ELSE 0结束

$query = DB::table('users AS u')
    ->join ('transactions AS t1', 't1.user_id', '=', 'u.id')
    ->selectRaw('
        u.id AS u_id,
        u.username AS u_username,
        SUM(CASE WHEN t1.currency = \'eur\' THEN t1.amount END) AS total_eur,
        SUM(CASE WHEN t1.currency = \'usd\' THEN t1.amount END) AS total_usd,
        SUM(CASE WHEN t1.currency = \'gbp\' THEN t1.amount END) AS total_gbp,
        SUM(CASE WHEN t1.currency = \'jpy\' THEN t1.amount END) AS total_jpy
    ')
    ->groupBy('u.id');

检查语法-我不使用Laravel

如果某些货币未列在某些用户数据中，您将得到NULL。如果您需要零，那么将表达式扩展到
CASE，当t1.currency=\'xxx\'时，则t1.amount ELSE 0结束
啊，所以我只需要
加入事务
一次？啊，所以我只需要
加入事务
一次？刚刚更新了我的代码，非常有魅力，谢谢！刚刚更新了我的代码，很有魅力，非常感谢！