aggregate data types general unpacked structure packed structure unpacked untagged unions packed untagged unions tagged union packed tagged union Summary usage of rand/randc in struct usage of rand/randc in union general Aggregate data type includes struct/union/array/queue A structure represents a collection of data type. By default, structures are unpacked When a packed dimension is used […]
Tag: aggregate
[Database] Explain clearly through examples, Mongodb’s addition, deletion, modification, group query, and aggregate query aggregate
Table of Contents 1. Basic concepts 2. Database management 1.Create database 2. Delete the database 2. Collection management 1. Show all collections 2. Create a collection 3. Delete the current collection 4. Insert elements into the collection 3. Document management 1. Document insertion 2.Update of documents 3. Deletion of documents 4.Document query (1) Basic query […]
[MySQL] aggregate function and group query
Article directory 1. Aggregation function 1.1 count returns the number of queried data 1.2 sum returns the sum of the queried data 1.3 avg returns the average value of the queried data 1.4 max returns the maximum value of the queried data 1.5 min returns the minimum value of the queried data Two, group query […]
Primary key, unique, default, non-null, check, foreign key constraint and aggregate function group query in mysql database
1. Constraint basic usage Constraints are rules that act on fields in a table to limit the data stored in the table. Purpose: To ensure the correctness, validity and integrity of the data in the database. Constraints are to ensure that the data entering the database is valid and reliable, and some constraints are imposed […]
Mongodb SQL to Aggregate Mapping Quick Reference
SQL Mapping Aggregation pipelines allow MongoDB to provide native aggregation functionality, corresponding to many common data aggregation operations in SQL. For example: GROUP BY, COUNT(), UNION ALL Test data For MySQL root@localhost 14:40:40 [test]> select * from orders; + —– + ——— + ——————— + ——- + — —– + |_id|cust_id|ord_date|price|status| + —– + ——— […]
Django-ORM add, delete, check and modify all explanations (full text), advanced query, F/Q object, single/multiple condition query, joint query, and/or query, aggregate query function, comparison query between fields, master table and slave table Query, foreign key constraint query, complex condition query, regular query
Django-ORM basic additions, deletions, checks and modifications Suggested reading order: add-query-update-delete It is recommended to look at the article directory on the right, and read it according to your needs! ! ! Basic project structure and fields data sheet: BookInfo table (book information table) RoleInfo table (character information table) Definition of tables in Models.py from […]
[MySQL] Basic query (insert query results, aggregate functions, group query)
Table of Contents 1. Insert query results 2. Aggregation function 3. Group by & having Fourth, the execution order of SQL queries Five, OJ practice 1. Insert query result grammar: INSERT INTO table_name [(column [, column …])] SELECT … Case: Delete duplicate data in a table –Create an initial repeating table mysql> CREATE TABLE duplicate_table […]
SQL database advanced query statement – deduplication, sorting, grouping query, aggregate function, grouping and comprehensive query
Advanced query – distint, order by, limit #`select` statement, you can use the `distinct` keyword to deduplicate the query result set. select distinct column 1, … , column n from table_name [other clauses]; #`order by` is used to sort and display the results, you can use `ASC` (ascending order) / `DESC` (descending order) to sort, […]
Database aggregate functions and window functions
1. Aggregation function Aggregate functions for a database are functions used to perform aggregate calculations on datasets. They take a set of values as input and produce a single aggregated value as output. Aggregate functions are often used in conjunction with the GROUP BY clause to perform aggregate operations based on grouping of data. 1.1. […]
Flink AggregateFunction window function, when to execute merge
1. Preface When we use the Flink DataStream API to write business code, the aggregate() operator and AggregateFunction are undoubtedly very commonly used. Writing an AggregateFunction needs to implement 4 methods: /* * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with […]