Class Diagram: SQL Query Builder

Classes:

1. QueryBuilder
2. User
3. DatabaseConnection
4. Query
5. Table
6. Column
7. Filter
8. Join
9. ExportService
10. AuthenticationService

Explanation of the Classes:

QueryBuilder:

• Central class responsible for building the SQL query.
• Manages tables, filters, and joins.
• Methods include:

• • • buildQuery(): Generates the SQL query.

    • addTable(), addFilter(), addJoin(): Add tables, filters, or joins to the query.

    • executeQuery(): Executes the generated SQL query.

User:

• Represents a user of the SQL Query Builder system.
• Contains username, password, and role (e.g., admin, analyst).
• User authentication is handled by the AuthenticationService.

AuthenticationService:

• Handles user login and role-based authentication.
• Method: authenticate(), which checks the user’s credentials.

DatabaseConnection:

• Represents the connection to the database where the query will be executed.
• This class would typically manage the connection pool and handle database interactions.

Query:

• Represents the generated SQL query.
• Contains the raw queryText and the result returned after execution.
• Method: execute(), which executes the query on the database.

Table:

• Represents a database table in the SQL query.
• Contains tableName and a list of columns.
• Method: addColumn(), which adds columns to the table.

Column:

• Represents a column in a table.
• Contains columnName and dataType.
• Provides a method to return the column name (getColumnName()).

Filter:

• Represents a filter or condition in the WHERE clause of the SQL query.
• Contains the condition as a string (e.g., “age > 30”).
• Method: apply(), which applies the filter to the query.

Join:

• Represents a JOIN operation in SQL (e.g., INNER JOIN, LEFT JOIN).
• Contains joinType (INNER, LEFT, etc.) and joinCondition.
• Method: applyJoin(), which adds the join to the SQL query.

ExportService:

• Responsible for exporting the query results into different formats (e.g., CSV, Excel).
• Method: export(), which exports the results in the specified format.

How to Explain to Your Students:

Start with the Core Class – QueryBuilder:

• This is the class that brings everything together. It builds and executes SQL queries based on user input.

Explain Relationships:

• QueryBuilder has relationships with Table, Filter, and Join classes to build SQL components like SELECT, WHERE, and JOIN clauses.
• The Query class holds the final query text and handles its execution.

Highlight the Role of User & Authentication:

• Users interact with the QueryBuilder. Their roles are managed by the AuthenticationService.

Show Interaction with Database:

• After building the query, the Query class handles its execution via the DatabaseConnection class.

Discuss Exporting Results:

• After executing the query, the ExportService allows exporting results in various formats.