graphical query language algorithms

My intention is to 开发者_开发问答write a graphical query language where users can drag and drop criteria into a GUI query designer, then the designer will generate appropriate SQL query code and return the appropriate result set. Do you know where I can learn more about SQL code generation or if similar tools like this exist?

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You may want to look at Microsoft Access's query designer to see how it works; it's relatively simple to use and you can compare how changes in the graphical representation affect the SQL statement and vice-versa. It should give you a pretty good view of how joins are translated into SQL.

(I cringe to suggest Microsoft Access for anything, but in this case, it might be useful to you).