[MySQL] Generate ERD in MySQL workbench
To present the solution design, Entity-Relationship Diagram (ERD) is still one of the common diagram to present data and its relationship. But it is the nightmary if draw it as it is complicated and human […]
To present the solution design, Entity-Relationship Diagram (ERD) is still one of the common diagram to present data and its relationship. But it is the nightmary if draw it as it is complicated and human […]
For tuning MySQL, normally it will check index scan, cache and any hardware allocation align with database or not. To measure it, there are several tools to support your judgement.
因為project 會從Java 轉移到.net 中, 趁此機會順便對Java JPA 有關的mapping 摘錄, 以便以後查看.
之前在Java 遇過同樣問題, 解決方案是在getter 中加入annotation. 而在.net core 中, 則需要透過修改startup().
利用MongoDB 在編程上帶來不少方便, 但稍一不慎就會令到結構變得難以複雜. 示範中會利用mongoDB 讀取collection 中的property name.
備份資料庫除了利用內部 SQL Server Agent 的schedule job 外, 還可以透過指令檔進行. 這樣的好處是可以透過中央化管理的形式去管理排程工作.
當rename database 時, 有時會出現elusive lock 問題. 這是因為執行時有其他user 正在使用而令database locked.
有時進行維護時, 總會須要將系統offline. 但有時會出現錯誤指TABLE 被Lock. 這是因為執行ALTER TABLE 時, 會見到有process 仍在執行.
有時當進行performance tuning 時, 有時會在ORM 層面遇到問題. 檢查記錄後, 發覺原來透過Entity Framework 將LINQ 或Lambla express 轉換成SQL 時會出產生了不必要的Check null, 從而使Index 不能觸發, 亦因此令執行時間變長.
利用SQL 制作report 時, 有時為了參考, 便在query 中加入 row no. 在Oracle 中, 可以透過hierarchy query 進行.
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