論“萬劍歸宗”思想對開發設計的一點“膚淺”作用

{"type":"doc","content":[{"type":"heading","attrs":{"align":null,"level":1},"content":[{"type":"text","text":"爲什麼叫“萬劍歸宗”？","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"這裏有一個富含仙俠中二氣息的霸氣名字：“","attrs":{}},{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"萬劍歸宗","attrs":{}},{"type":"text","text":"”","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"這其實只是爲了忽悠大家注意力而故意取得名字，","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"實際上就是","attrs":{}}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"機器學習中大家說的比較多的 歸一化 （參考 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三個國家都起作用","attrs":{}}]}],"attrs":{}},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":6,"align":null,"origin":null},"content":[{"type":"text","text":"需要保存新的賬號關聯關係","attrs":{}}]}],"attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":6,"align":null,"origin":null},"content":[{"type":"text","text":"總結：核心問題在於實現保存賬號關聯關係","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"樸實無華的設計","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"這時候小白同學已經明白了一切根本焦點 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表也不需要寫數據","attrs":{}}]}],"attrs":{}},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":5,"align":null,"origin":null},"content":[{"type":"text","text":"會員表原來就會記錄哪個賬號是會員，join一下mapping表，就可以拿到玩家所有的會員賬號了，簡單","attrs":{}}]}],"attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":5,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":5,"align":null,"origin":null},"content":[{"type":"text","text":"最後 PlayerMapping 表就是這樣","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"| id | USAPlayer | ChinaPlayer | CANPlayer |","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"| ----| ---- | ---- | ---- |","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"| 1 | Gold | Shen | girl |","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"| 2 | Gddd | Sddd | null |","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"看起來好像也沒啥大問題，雖然感覺要新加國家會加字段這點非常彆扭","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"實際使用","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"這裏爲了簡單，就只舉sql僞碼的兩個例子說明：","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"新增mapping關係","attrs":{}}]},{"type":"codeblock","attrs":{"lang":"sql"},"content":[{"type":"text","text":"IF not EXISTS(select top 1 1 from [dbo].[PlayerMapping] C WITH(NOLOCK)\nON c.USAPlayer = @Player OR c.ChinaPlayer = @Player OR c.CANPlayer = @Player)\nBEGIN\n\n insert into [dbo].[PlayerMapping]\n (\n USAPlayer \n ,ChinaPlayer \n ,CANPlayer \n )\n select CASE when @Country = 'USA' then @Player when @MappingCountry = 'USA' then @MappingPlayer else null end,\n CASE when @Country = 'China' then @Player when @MappingCountry = 'China' then @MappingPlayer else null end,\n CASE when @Country = 'CAN' then @Player when @MappingCountry = 'CAN' then @MappingPlayer else null end\n\nelse \n UPDATE c \n set c.USAPlayer = CASE when @Country = 'USA' then @Player when @MappingCountry = 'USA' then @MappingPlayer else c.USAPlayer end,\n c.ChinaPlayer= CASE when @Country = 'China' then @Player when @MappingCountry = 'China' then @MappingPlayer else c.ChinaPlayer end,\n c.CANPlayer = CASE when @Country = 'CAN' then @Player when @MappingCountry = 'CAN' then @MappingPlayer else c.CANPlayer end\n from [dbo].[PlayerMapping] c\n where c.USAPlayer = @Player OR c.ChinaPlayer = @Player OR c.CANPlayer = @Player\nend ","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"查找所有有會員折扣的賬號信息","attrs":{}}]},{"type":"codeblock","attrs":{"lang":"sql"},"content":[{"type":"text","text":"DECLARE @Players table \n(\n USAPlayer varCHAR(60)\n ,ChinaPlayer varCHAR(60)\n ,CANPlayer varCHAR(60)\n ,Discount DECIMAL(18,2)\n)\n\nINSERT INTO @Players\n(\n Discount\n ,USAPlayer\n ,ChinaPlayer\n ,CANPlayer\n)\nSELECT \n A.Discount\n ,CASE when A.Country = 'USA' then A.Player else isnull(c.USAPlayer,'') end\n ,CASE when A.Country = 'China' then A.Player else isnull(C.ChinaPlayer,'') end\n ,CASE when A.Country = 'CAN' then A.Player else isnull(c.CANPlayer,'') end\nFROM dbo.Player A WITH(NOLOCK) \nLEFT JOIN [dbo].[PlayerMapping] C WITH(NOLOCK)\nON c.USAPlayer = A.Player OR c.ChinaPlayer = A.Player OR c.CANPlayer = A.Player\nWHERE A.Status='會員'\n\nSELECT DISTINCT\n Discount\n ,Player\nFROM (\nSELECT \n Discount\n ,USAPlayer AS Player\nFROM @Players\nWHERE USAPlayer <> ''\nUNION ALL\nSELECT \n Discount\n ,ChinaPlayer AS Player\nFROM @Players\nWHERE ChinaPlayer <> ''\nUNION ALL\nSELECT \n Discount\n ,CANPlayer AS Player\nFROM @Players\nWHERE CANPlayer <> ''\n) A\n","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"en.... ","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"是不是大家都覺得這兩段sql 都挺複雜的呢？","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"可能是作者sql功力不行，大家可以試試看能不能寫出在這樣設計下更好更快更簡單的sql呢？","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":1},"content":[{"type":"text","text":"如果重頭用\"萬劍歸宗\"來思考呢？","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"好吧，其實我們是用 ","attrs":{}},{"type":"link","attrs":{"href":"https://zh.wikipedia.org/wiki/%E7%A9%B7%E4%B8%BE%E6%B3%95","title":""},"content":[{"type":"text","text":"窮舉法","attrs":{}}]},{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":" 和","attrs":{}},{"type":"link","attrs":{"href":"https://zh.wikipedia.org/wiki/%E6%95%B0%E5%AD%A6%E5%BD%92%E7%BA%B3%E6%B3%95","title":""},"content":[{"type":"text","text":"數學歸納法","attrs":{}}]},{"type":"text","text":"來思考","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"大家都知道 窮舉法 實際是一種數學證明法，","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"一個證明法怎麼能幫助我們思考呢？","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"當然是直接不行，但它可以用來證明我們想法簡不簡單，好不好用","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"比如上面樸實無華的設計","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"如何用 窮舉法 證明設計是不是簡明？","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"我們設計 mapping 表的目的是爲了幫助我們找到用戶實際有多少個賬號，","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"那麼我們需要證明的命題就是當 mapping 表 有N條mapping 記錄時能幫我們用一個player名字找到實際有多少個賬號","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"假設 這個player 叫 Gold","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"當N = 0，mapping表不存在 Gold，找到賬號爲0 , 不對勁，玩家肯定得有個賬號，否則Gold 從那裏來？ ","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"當N= 1， mapping 記錄有三個字段 USAPlayer，ChinaPlayer， CANPlayer， 無法確定Gold唯一確定規則，只能其中一個等於Gold 就算有效","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"如上，每一個證明，我們都沒辦法直接用最簡單的條件確定，要不得已用多餘的規則確定","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"所以根據以上問題，我們可以嘗試做出如下調整","attrs":{}}]},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"當N = 0，mapping表不存在 Gold，找到賬號爲0 , 不對勁，玩家肯定得有個賬號，否則Gold 從那裏來？","attrs":{}}]}],"attrs":{}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"那麼我們保證即使玩家只有一個賬號，mapping 表也有數據，那麼 N=0的情況不存在了，那麼也是證明有效","attrs":{}}]},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"當N= 1， mapping 記錄有三個字段 USAPlayer，ChinaPlayer， CANPlayer， 無法確定Gold唯一確定規則，只能其中一個等於Gold 就算有效","attrs":{}}]}],"attrs":{}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"問題出在有三個字段，那麼我們把","attrs":{}},{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"三個字段砍成一個字段","attrs":{}},{"type":"text","text":"不就解決這個問題了嗎？","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"PlayerMapping 表就是這樣","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"| id | Player | ","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"| ----| ---- | ","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"| 1 | Gold | ","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"| 2 | Gddd | ","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"| 3 | Shen |","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"| 4 | girl |","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"| 5 | Sddd |","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"但是這樣好像無法mapping，應該加mapping 綁定id 去確定關係，就是這樣","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"| id | Player | MappingId |","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"| ----| ---- | ---- |","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"| 1 | Gold | M |","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"| 3 | Shen | M |","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"| 4 | girl | M |","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"這樣再次套用窮舉法：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"假設 這個player 叫 Gold，MappingId 都爲M","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"當N = 0， 不存在這樣情況，證明成立","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"當N= 1，那必定只有一條 Gold ，證明成立","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"當N=2， Gold 對應的MappingId 可以找賬號信息，證明成立","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"當N=3， Gold 對應的MappingId 可以找賬號信息，證明成立","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"當N=4，一個玩家暫時沒有那麼過country，證明成立","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"當N= 。。。。。 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證明設計是不是簡明？","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"其實吧，對我們程序員來說，","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"我們不是數學家，我們不需要寫什麼證明式，","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"我們的證明式其實就是我們的程序，","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"比如上面的命題","attrs":{}}]},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"當 mapping 表 有N條mapping 記錄時能幫我們用一個player名字找到實際有多少個賬號","attrs":{}}]}],"attrs":{}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"我們按照現在的mapping 表 設計","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"| id | Player | MappingId |","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"| ----| ---- | ---- |","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"| 1 | Gold | M1 |","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"| 2 | Gddd | M2 |","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"| 3 | Shen | M1 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我們自己看出合不合理，簡明不簡明，實在不行還可以跑程序測試","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"當然如果我們寫不出這樣的sql，必須添加if else ，那必然是我們方案還存在一些特殊情況，這種時候就需要我們自行取捨，找到一個平衡的點","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"新方案實際使用","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"新增mapping關係","attrs":{}}]},{"type":"codeblock","attrs":{"lang":"sql"},"content":[{"type":"text","text":"declare @mappingid VARCHAR(60) = SELECT top 1 mappingid from [dbo].[PlayerMapping] C WITH(NOLOCK) where c.Player = @Player\n\nIF(@mappingid IS NULL)\nBEGIN\nSET @mappingid = UUID()\nEND\n\ninsert into [dbo].[PlayerMapping]\n (\n Player \n ,MappingId \n )\n select 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A.Status='會員'","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":1},"content":[{"type":"text","text":"總結","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"其實說了那麼多，大家是不是已經發現了，","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"什麼 窮舉法啊 數學歸納法啊 從初中開始，","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"我們都是學過的，","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"並且我們經常做事情也是這樣做的，","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"但是爲什麼我們卻時常做出東東總是差別人家孩子那麼一丟丟呢？","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"個人覺得還是我們心中差了一個字： 靜","attrs":{}}]}]}