Basic syntax of MySQL database

Basic operation of MySQL database 1. Creation of database 1.1 create database Create database create database <Database name>   -- stay sql Statements are not case sensitive Use database use <Database name> Delete database drop database  <Database name> view the database show databases <Database name> 1.2 crea ...

Posted by IG88 on Sat, 30 Apr 2022 18:54:06 +0300

Develop a big data SQL Engine that does not need to be rewritten as Hive QL

This article is shared from Huawei cloud community "developing big data SQL Engine from scratch", author: JavaEdge. Learn the core principles of big data technology, master some efficient ways of thinking and thinking, and build your own technical knowledge system. We can deduce and even realize various principles without understand ...

Posted by simonyuriko on Fri, 29 Apr 2022 17:24:06 +0300

Flink SQL combines Kafka, Elasticsearch and Kibana to analyze the behavior of e-commerce users in real time

Use flink sql to combine kafka, elasticsearch and kibana, real-time analysis of e-commerce user behavior One of the differences between Flink and other real-time computing tools is that it provides users with more abstract and easy-to-use APIs, such as connector interface, Table API and SQL for reading and writing various programs. All operati ...

Posted by sulin on Thu, 28 Apr 2022 13:02:57 +0300

(the most complete SQL statement, without one!) Explain SQL statement syntax in detail according to classification

catalogue 1, Foundation 1. Description: create database 2. Description: delete database 4. Description: create a new table 5. Create a new table based on the existing table: 6. Description: add a column 7. Description: add primary key: 8. Index creation Description: 9. Description: create view: 10. Several basic sql statements 11. De ...

Posted by fatherlyons on Thu, 28 Apr 2022 09:06:55 +0300

How to use SQL AND, OR, IN and NOT to filter the returned data

This paper introduces how to combine AND and OR operators into WHERE clause to establish more powerful AND advanced search conditions. We also showed how to use the NOT AND IN operators. 1, Combine WHERE clause stay How to use SQL WHERE to filter the returned data All WHERE clauses described in use a single condition when filtering data. For s ...

Posted by poelinca on Wed, 27 Apr 2022 07:06:56 +0300

Chapter 124 SQL function SECOND

Chapter 124 SQL function SECOND A time function that returns the number of seconds of a datetime expression. outline {fn SECOND(time-expression)} parameter Time expression - an expression that is a column name, the result of another scalar function, or a string or numeric literal. It must resolve to a TimeStamp string or a $HOROLOG st ...

Posted by markyoung1984 on Wed, 27 Apr 2022 04:40:43 +0300

sql statement exercise 50 questions (Mysql version)

sql statement exercise 50 questions (Mysql version) Table names and fields –1. Student list Student(s_id,s_name,s_birth,s_sex) -- student number, student name, date of birth, student gender –2. Class Schedule Card Course(c_id,c_name,t_id) --- course number, course name, teacher number –3. Teacher table Teacher(t_id,t_name) - ...

Posted by cosminb on Tue, 26 Apr 2022 22:49:55 +0300

[SQL Basics: getting to know database and SQL] installation and basic introduction notes

This note is the learning content of Alibaba cloud Tianchi Longzhu program SQL training camp. The link is: https://tianchi.aliyun.com/specials/promotion/aicampsql . 1, First knowledge database Database is a data set that can be accessed efficiently by saving a large amount of data and processing it by computer. This data set is called a d ...

Posted by kellog on Tue, 26 Apr 2022 20:02:43 +0300

Use of JDBC connection pool

JDBC 1, Database connection pool 1. Concept of database connection pool Database connection background Database connection is a key, limited and expensive resource, which is particularly prominent in multi-user web applications. The management of database connection can significantly affect the scalability and robustness of the whole appl ...

Posted by Drakkie on Sun, 24 Apr 2022 22:34:23 +0300

6-string function

String function: 1.1 string merging concat and concat_ws 1.2 string comparison strcmp 1.3 string length, char_length 1.4 case conversion lower and upper 1.5 string lookup 1.6 string interception substring 1.7 remove the leading and trailing spaces of the string 1.8 replacement string String function: . 1 string merging concat, concat_ws ① conc ...

Posted by belphegor on Sun, 24 Apr 2022 22:30:37 +0300