什么是事务?
事务是指是程序中一系列严密的逻辑操作,而且所有操作必须全部成功完成,否则在每个操作中所作的所有更改都会被撤消。可以通俗理解为:就是把多件事情当做一件事情来处理,好比大家同在一条船上,要活一起活,要完一起完.
事物的四个特性(ACID)
● 原子性(Atomicity)
● 一致性(Consistency)
● 隔离性(Isolation)
● 持久性(Durability)
执行count(1)、count(*) 与 count(列名) 到底有什么区别
behavior questions:
- how your manager judge about you during your previous job?
- What’s your experience about a project that fails, and how would you redo the project?
- What’s your Advantages and disadvantages in your personality?
- What’s your best project and why you did better than others in your opinion?
- What’s your plan about your future career?
tech questions:
- a problem of top k problem
- RMDB vs NoSQL DB
- Why distributed NoSQL DB cannot always support transaction?
- Level traverse a binary tree in an online white board.
- random questions about spark, hadoop etc
- How os’ thread works?
- General DWH concepts, Spark internals, mapreduce
- Explain the map reduce paradigm
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