Tag：Sentence
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Time：2019-12-8
select Select is a common keyword in go language. Linux has introduced this function for a long time to realize a non blocking way. A select statement is used to select which case the send or receive operation can be executed immediately. It is similar to the switch statement, but its case involves channel related […]
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Time：2019-12-5
SQL wildcard SQL wildcards can replace one or more characters when searching for data in a database. The SQL wildcard must be used with the like operator. In SQL, you can use the following wildcards: wildcard describe % Replace one or more characters _ Replace only one character [charlist] Any single character in a character […]
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Time：2019-11-29
Author: Huyan ten juejin.im/post/5d351303f265da1bd30596f9 Preface The main audience of this article is developers, so it doesn’t involve MySQL service deployment and other operations, and there are many contents. Everyone is ready for patience and melon seed mineral water A while ago, I studied MySQL systematically, and I also had some practical experience. I came across […]
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Time：2019-11-27
Dbutils is a simplified development kit for JDBC. You need to import commons-dbutils-1.6.jar to use dbutils normally. 1. Introduction to dbutils function 1. Queryrunner provides an API for SQL statement operations 2. The resultsethandler interface is used to define how to encapsulate the result set after the select operation 3. Dbutils class, a tool class, […]
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Time：2019-11-26
Preface The text and pictures of the article are from the Internet, only for learning and communication, and do not have any commercial use. The copyright belongs to the original author. If you have any questions, please contact us in time for handling. Author: PK Ge PS: if you need Python learning materials, you can […]
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Time：2019-11-26
Ruby is a very expressive language, which is proud of its extremely rich operators and syntax sugar. Although ruby has always regarded the principle of least surprise as one of its philosophies, it still often sees surprising and hard to understand code, which may be caused by the incomprehension of its operators and statement priorities. […]
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Time：2019-11-25
I. background: Due to the poor foundation of programming, I recently started to consolidate the learning of C foundation. In the later stage, I will summarize my own learning and summarize the corresponding articles. If there is any deficiency, please give me more advice. Two, introduction C ා the following types of judgment statements are […]
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Time：2019-11-24
Into usage: DECLARE a NUMBER; b number; c number;BEGIN SELECT MAX(SAL),MIN(SAL),AVG(SAL) INTO A,B,C FROM EMP;DBMS | output. Put | line (‘maximum wage: ‘| a);DBMS | output. Put | line (‘minimum wage: ‘| b);DBMS | output. Put | line (‘average wage: ‘| C);END; If statement DECLARE score NUMBER := 90;BEGIN IF score < […]
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Time：2019-11-24
I. background: Due to the poor foundation of programming, I recently started to consolidate the learning of C foundation. In the later stage, I will summarize my own learning and summarize the corresponding articles. If there is any deficiency, please give me more advice. Two, introduction Sometimes, you may need to execute the same piece […]
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Time：2019-11-24
Contents of this section: 1) index basis 2) index type (hash index, ordered array, B + tree) 3) some common problems of index 1) joint index 2) leftmost prefix principle 3) coverage index 4) index push down 1. Index basis Index plays an important role in query speed. Understanding index is also the starting point […]
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Time：2019-11-22
I. Introduction A for loop is a repetitive control structure that allows a written loop to execute a specific number of times. Two. Grammar For (expression1; expression2; expression3) { Circulatory body; } Here is the control flow for the for loop: Expression 1Will be executed first and only once. This step allows you to declare […]
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Time：2019-11-17
I believe that everyone has been exposed to MySQL database and will definitely write SQL. I don’t know if you feel this way. Anyway, I have such an idea. It is when I finish writing an SQL statement and execute it to get the desired result. At this time, I was wondering why I can […]
