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Summarized from database principle and application (MySQL Edition) Tsinghua University Press #In syntax, [] indicates that this part is optional, < > indicates that this part is required, and is not written when writing specific commands, # as a single line comment, / * * / multiple lines 1, Data definition 1. Create database CREATE ...

1.1 dba_ start dba_users            Database user information dba_segments         Table segment information dba_extents          Data area information dba_objects          Dat ...

1.SQL function 1.1 type detection function toTypeName select toTypeName(0); -- UInt8 select toTypeName(-0); -- UInt8 select toTypeName(1000); -- UInt16 select toTypeName(-1000); -- Int16 select toTypeName(10000000); -- UInt32 select toTypeName(-10000000); -- Int32 select toTypeName(1.99); -- Float64 select toTypeName(toFloat32(1.99)); ...

testrecord database stores player behavior records, which need to be cleaned up every three months. Preparation before deleting data To view the size of the testrecord database: MySQL [(none)]> USE information_schema; Database changed MySQL [information_schema]> SELECT CONCAT(ROUND(SUM(DATA_LENGTH/1024/1024/1024),2),'GB') -> a ...

1, Foreword MyBatis is a very popular ORM framework at present. Its function is very powerful, but its implementation is relatively simple and elegant. This paper mainly describes the architecture design idea of MyBatis, discusses several core components of MyBatis, and then explores the implementation of MyBatis by combining a select quer ...

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All database learning summary articles are summarized according to the shangsilicon Valley video of station B, and the video links are as follows: [https://www.bilibili.com/video/BV12b411K7Zu] Data definition language is mainly used for Library and table management. CREATE keyword: CREATE Modify keyword: ALTER Delete keyword: DROP 1 ...

data typeDQL languageDML languageDDL languageDCL languageTCL languageNon foreign key constraintForeign key constraintForeign key policyDDL and DML add a littleMulti table query syntaxSubqueryaffairTransaction concurrency problemTransaction isolation levelView + stored procedureJDBC+sql injection + other Installation: uninstall all mysql and ma ...

preface In the previous chapters, I only learned about the principles of using indexes and what indexes to use with the explain keyword. The next two chapters consider how to make better use of indexes. Example table drop table `employees`; CREATE TABLE `employees` ( `id` int(11) NOT NULL AUTO_INCREMENT, `name` varchar(24) NOT NULL ...

I. MyBatis Loading Policy 1. What is delayed loading? Problem: Configuration and implementation of one-to-one, one-to-many, many-to-many relationships in Mybatis is achievable Object's associated query. Many times in the actual development process we don't always need to load user information before we have to load his order information. This ...