C#实现SQL查询分析器(C# Visual SQL Query Designer)

Introduction

This article describes the implementation of a QueryDesignerDialog class that allows users to create SQL queries based on a given OLEDB connection string.

The designer is similar to the ones found in database tools such as the SQL Server Management Studio and Microsoft Access. It allows end users to build SQL queries with support for sorting, grouping, and filtering.

The main limitation of the QueryDesignerDialog is that it does not parse existing SQL statements. This is a one-way tool; you can use it to create new queries, but not to edit existing ones. Also, it only supports OLEDB data sources, which includes SQL Server and Access. Future versions may address these limitations.

Background

The first version of the QueryDesignerDialog was written for use with a Report Designer application. I could not find a tool (free or commercial) to do the job the way I wanted, so I decided to write it myself. After that, I re-used it in a few other applications, and thought it might be useful to others as well.

Using the Code

The QueryDesignerDialog has two main properties:

• ConnectionString: Gets or sets the OLEDB connection string used to retrieve the database schema with the list of tables, views, fields, and relations from which the query will be built.
• SelectStatement: Gets the SQL statement designed by the user. For now, this is a read-only property. The dialog cannot be used to edit existing SQL statements. Perhaps this will be added in future versions.

The code snippet below shows how the QueryDesignerDialog is typically used. You assign it a connection string, show the dialog, and read back the SQL query:

代码: 

This code invokes the "DataLink" dialog seen below:

打开"DataLink"对话框