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08 multi table query 1, Multi table query 1. Cartesian set 2, Oracle connection 1. Equivalent connection 2. Multiple join conditions AND and operators 1. Distinguish duplicate column names 2. Alias of table 3. Multi table associated query 4. Non equivalent connection 5. external connection 1. Int ...

Catalog Usage scenarios The essence of builder mode Code example Code call Usage scenarios - we want to build a complex product. For example: Shenzhou spaceship, Iphone. The creation of this complex product. There is a problem that needs to be addressed: • is there a step problem in assembl ...

Still using mysql for full-text indexing? Try elastic search! Note: the following documents are based on elasticsearch version 7. X, which is different from the old version 1. Format description The data interaction interface of elasticSearch is based on http protocol, and the basic format is as fol ...

1 Definition Window function, also known as analysis function Analytic functions compute an aggregate value based on a group of rows. They differ from aggregate functions in that they return multiple rows for each group. The group of rows is called a window and is defined by the analytic_clause.Th ...

A friend on motianlun encountered a rare ORA-600 error. The first error parameter is KGLDELETEALLPINSONOBJ1. From the naming of KGLDELETEALLPINSONOBJ1, we can quickly guess the basic situation: KGL - Kernel Generic Library cache, which means that the problem lies in the Library Cache level; DELET ...

What is Hibernate: Hibernate is an open-source object relational mapping framework, which encapsulates JDBC with very lightweight objects. It establishes the mapping relationship between POJO and database tables. It is a fully automatic ORM framework. Hibernate can automatically generate SQL statement ...

Overview of IO - what is IO (input, output) - what is a set of orderly data sets with start and end points, such as file flow, network flow, etc - difference from file: file is a static data presentation, and flow is a dynamic concept The operation of data in Java is carried out in the way of flow. The ...

Today, I will continue to introduce the related functions of Java Web twitter project, mainly the selfdetail.jsp interface Modify background map function <button class="btn btn-info" id="xiugaibg">Click to modify the background map</button> <form action="" method="post" id="updatebg" e ...

In the actual development, we always use paging query. Different database paging SQL methods are different. We can use paging plug-ins to help us separate queries. We only need to care about the data itself, not the place 1. Plug in introduction Configure the paging plug-in in the core configuratio ...

In the previous section, the creation of the main interface is completed. In this section, the function of adding book categories will be realized. The BookTypeAddPanel.java class file has been successfully created in the previous section, so you can write code directly in the file. Since the databa ...