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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:

  1. how your manager judge about you during your previous job?
  2. What’s your experience about a project that fails, and how would you redo the project?
  3. What’s your Advantages and disadvantages in your personality?
  4. What’s your best project and why you did better than others in your opinion?
  5. What’s your plan about your future career?

tech questions:

  1. a problem of top k problem
  2. RMDB vs NoSQL DB
  3. Why distributed NoSQL DB cannot always support transaction?
  4. Level traverse a binary tree in an online white board.
  5. random questions about spark, hadoop etc
  6. How os’ thread works?
  7. General DWH concepts, Spark internals, mapreduce
  8. Explain the map reduce paradigm

Reference