JOIN operations are staple techniques in relational databases that enable the amalgamation of data that is present in two or more tables based on the keys that are present in every table. It is vital to master the different kinds of JOINs to improve query operations and obtain the right set of data for one’s application. This article will introduce the various categories of JOIN operations and discuss cases of their usage, as well as how they are used in DBMS. 

1. Inner Join 

Inner Join also referred to as EQ JOIN is the most used join operation among all the other types of join. That means that the records in the first table it matches those records containing similar values in the second table of the join. This means that the query returns only the rows that have matches in the stated columns i and a row-by-row comparison returns a row if the specified columns are an exact match. 

Use Case: In simple terms, Inner Joins are commonly used when one is interested in a record that has corresponding data in another table. For instance, consider you want to mine customers who have placed orders containing specific information, you need to join the Customers table with the Order table concerning their joining key, say CustomerID. 

2. Left (Outer) Join 

A Left Join shall give us all records from the left table as well as the records that match in the right table. If there are no records the returned value is NULL on the right table of the join. 

Use Case: Left joins are applicable if one is interested in all records in one table irrespective of the records which may not be there in the other table. For instance, you may decide to use what you have learned about the Left Join to generate a list of employees together with the department names that they belong to, or the lack thereof if some of the employees are without a department yet. 

3. Right (Outer) Join 

Right Join operates similarly to left join except that in the result all records of the right table are included along with the matched records in the left table. If no match is possible the result is NULL on the side of the left table. 

Use Case: Right Joins are not very popular as Right Joins are used when the user requires all the entries of the right table no matter if they have a matching element in the left table or not. An example might be listing all sales records and including all the details of the salespersons even if there are any that have not made a single sale. 

4. Full (Outer) Join 

A Full Join returns all records when there is a match in either of the tables or else a null record is placed. It is a mixture of Left and Right Join where all the records of the table on the right side having matching data are included. 

Use Case: Full Joins are used when you have to get all the records from both tables irrespective of whether it is a match or not. This may prove useful when, for example, ingesting data from two distinct systems and you need to retain all the records for more analysis, e.g., when comparing and contrasting transactional data from two dissimilar systems. 

5. Cross Join 

Cross Join on the other hand will return every record in Table 1 combined with every record in Table 2. This join does not depend on any condition to be met. 

Use Case: Cross joins are not very popular in practice mainly due to their capability to produce a large number of rows but they can be used in producing all combinations of two sets of values. For instance, if you wish to have a list of all possible products that can be of a certain color in a store, then applying the Cross Join type will suffice. 

6. Self Join 

Self Join is similar to an inner join except for the fact that in this method of joining the table is joined with itself. This is useful when dealing with items that are organized in a hierarchical form where a record in a table is related to another record within the same table. 

Use Case: Self Joins are also applied to get data that is connected in a tiered manner or a parental manner. For instance, while developing an application that involves employee information storage you will want to retrieve, all employees and their superiors from the same table using Self Join.

Implementations in CRUD Processes 

JOIN operations are very important in database management, especially in performing CRUD operations that involve operations between several related tables. For example, if one is developing CRUD operations in. , LINQ And Stored Procedures, when utilizing NET Core, Inner Join to retrieve the needed data for the user interface or LEFT Join so that the data can be retrieved even if some of the related information is missing. 

Likewise, while performing more complex operations such as filters and Sooners, it becomes relevant to know how different join types affect the data set. For example, in Java Streams API, when the concept of transforming or filtering data is adopted, it can be said to bear some resemblance to how records from different tables are joined and filtered in SQL. 

 To learn more about the ways that can be used JOIN operations in a given programming environment, for example, to carry out CRUD operations with ASP. NET MVC and AJAX.