• How to know which tables in the database have no records


    Use SP? Msforeachtable, the system stored procedure. Create a temporary table with 2 fields, [table name] and [total records]. Then use sp ﹣ msforeachtable to process and insert the result into the temporary table created above. If the total “records is 0, there are no records in this table.   DROP TABLE #Temp_T GO CREATE […]

  • How much do you know about border radius?


    Before the appearance of the CSS3 property border radius, we must draw a circle on the page with the help of pictures. After the border radius property, it is very easy for us to realize a circle on the page. Next, let’s study this border radius carefully to see what kind of black magic does […]

  • Apache Flink zero basic introduction (4): five modes of client operation


    Author: Zhou Kaibo 1. Environmental description In the previous several courses, I talked about the building of Flink development environment, the deployment and operation of applications. Today’s course is mainly about the client operation of Flink. This explanation focuses on practical operation. This course is community-based Flink version 1.7.2. The operating system is Mac, and […]

  • Java Concurrent synchronized keyword and lock interface


    Welcome to like reading, study and exchange together, please leave a message if you have any questions.Open source javahouse is also available on GitHub. Welcome to star Quote During the development process, we encountered concurrency problems. How to solve it? One solution, simple and crude: lock. Stop thousands of troops and horses. Only one person […]

  • [PHP] redis based distributed lock to prevent high concurrent and repeated requests


    Demand:First, let’s take a list of system validation: (a channel system, B business system, C system of external manufacturers)(1) B business system calls channel a system to verify whether the three elements of incoming mobile phone, ID card and name are consistent.(2) A channel system calls external manufacturer C system.(3) Channel a system returns the […]

  • [] = =! [] what happened?


    I can’t remember seeing this comparison somewhere. At that time, I didn’t have a clear understanding of forced conversion, so I have this article. Think I’ll expand with the title expression? Then you are wrong. How to convert [] = [] directly: Because the priority of the! Operator is high, run [] on the right […]

  • iterator & generator


    1. Basic knowledge: Iterator iterator is to solve the tedious problem of multi-level loop nesting and traversal. Generator is a function that returns iterator and can control asynchronous execution well. 2. Generator controls asynchronous execution: eg: function run(taskFun) { var task = taskFun(); //Start objective function var result = task.next(); //Recursive call next execution function […]

  • Apache Flink zero basic introduction (8): SQL programming practice


    Author: Wu Zhen (Yunxie) This is the eighth article in the Apache Flink zero Basics series, which will explain the programming practice of Flink SQL through five examples. Note: this tutorial is based on the open source SQL training project of ververica. Based on Flink 1.7.2. What can you learn from this lesson? This article […]

  • MySQL stored procedure 02


    This time, I will continue to talk about MySQL stored procedures: Let’s first look at its multi branch control structure case: The case statement is simple: Case variable name When condition 1 then output result 1; When condition 2 then output result 2; …… end case;   Let’s create a stored procedure to implement it: […]

  • Interesting knowledge in JS


    1. Semicolon and line break function fn1(){ return { name: ‘javascript’ }; } function fn2(){ return { name: ‘javascript’ }; } var obj1 = fn1(); var obj2 = fn2(); console.log(obj1); console.log(obj2); This example doesn’t look different, but in essence, it is. The first output is an object and the second is undefined. Why? Because there […]

  • Explain Oracle paging query with simple example


    What is paging query Paging query is toqueryThe result set to is displayed by page. For example, a result set has 1W rows and 100 databases per page. And you get the result set on page 2. Why pagination query If a result set has dozens of W lines, the display on a page will […]

  • Simple implementation of JDBC paging query


    JDBC paging query source code /** *Paging query * *@ param SQL paging query statement *@ param page (minimum 1) *@ param PageSize */ public void pageQuery(String sql,int pageSize, int page) { Connection conn = null; Statement st = null; ResultSet rs = null; RowSetFactory factory = null; try { //Get connection to database conn […]