Getting table schema from a query

Question

As per MSDN, SqlDataReader.GetSchemaTable returns column metadata for the query executed. I am wondering is there a similar method that will give table metadata

Answer 1

It's almost like you need a parser to parse the SQL and then from the parsed query make a symbol table of aliases and the tables they refer to. Then combine that with the results of GetSchemaTable() so that you can map columns to the appropriate alias.

Anyway see the question Parsing SQL code in C# for some parsers. I haven't looked at them in detail but maybe one of them is what you need. If you are only doing select statements check out the ANTLR link and the grammar for http://www.antlr.org/grammar/1062280680642/MS_SQL_SELECT.html.

If your queries are simple, you could probably use regular expressions or your own custom grammar to parse out the aliases and table names from the query. This would probably be the easiest solution.

The most robust solution is probably to pay for someone else's parser that handles full SQL and breaks it up into a parse tree or something else where you can query it. I'm not sure the merits of each one and the price/robustness ratio. But some of them are ultra expensive.... I would say if you can't do it yourself explore the ANTLR grammar (because it is free) assuming you just need select statements. Otherwise you may have to pay....

Actually assuming your users aren't crazy SQL geniuses and using subqueries/etc. I don't see why you can't use the table names from the schema view that you said you got to find them in the query and then find the alias as either tablename alias or tablename as alias. That might work for many of the cases.... But for the full general case you'd need a full parser.....