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sql execution statement flow analysis The whole processing flow is in exec_simple_query function. The code structure is as follows: /* * exec_simple_query * * Execute a "simple Query" protocol message. */ static void exec_simple_query(const char *query_string) { ... //Original syntax tree acquisition /* * Do basic parsing of the quer ...

Title: there are two tablesTable 1: Sales details   Table 2: product details Demand: query the monthly sales in 2020 and the year-on-year comparison, and sort them in ascending order by month and year Idea: step by step operation Get monthly dataFirst, the extraction time and the sales of each month. To have sales, the two tables must b ...

Write in front: This article is my study record. If there are mistakes, please point them out and correct them immediately DDL, DQL, DML and DCL will be written in four parts, and DQL will be written in this article. What is DQL? DQL: data query language, used to query data First, paste a table, and the following query contents will be us ...

1. Requirements id start_time end_time 1001 2021-12-01 08:08:05 2021-12-01 19:02:07 1002 2021-12-01 08:15:07 2021-12-01 19:05:10 1003 2021-12-01 09:10:20 2021-12-01 21:02:07 1005 2021-12-01 09:26:05 2021-12-01 19:52:15 1006 2021-12-01 10:08:05 2021-12-01 22:05:06 1004 2021-12-01 10:20:07 2021-12-01 18 ...

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prefacePostgresSQL is a single example multi database. Usually, a database instance contains multiple tablespaces and databases. One tablespace can store multiple databases. In this relationship, one tablespace can contain multiple databases, but a database can only belong to one tablespace and cannot be stored across tablespaces. Table space i ...

Answer #11: what is the difference between char and varchar in MySQL1. Experimental scenarioGreatSQL 8.0.25 InnoDB2. Experimental test2.1 differencesparametercharvarcharIs the length variableFixed lengthLengthenstorage capacity 0 ~ 2550 ~ 65,5352.2 construction test tableCREATE TABLE vc (v VARCHAR(4), c CHAR(4));2.3 test without exceeding the s ...

This note is the learning content of Alibaba cloud Tianchi Longzhu plan SQL training camp. The link is: https://tianchi.aliyun.com/specials/promotion/aicampsql preface This note is the learning content of Alibaba cloud Tianchi Longzhu plan SQL training camp. The link is: https://tianchi.aliyun.com/specials/promotion/aicampsql Dataset ...

Why write unit tests When talking about test cases, many people's first reaction is that our company's tests will write test cases, and I will also use postman or swagger for code self-test. Should we write unit test cases? Referring to Alibaba's development manual, rule 8 (the basic goal of unit testing: the statement coverage rate should re ...

Create a sequence table in the database to record the maximum id currently occupied. Each client host takes an id interval (for example, 1000-2000) to cache locally and updates the id maximum record in the sequence table. Client hosts take different id intervals, run out and retrieve, and use the optimistic locking mechanism to control concurre ...