Can a Free Parser Generate a Tree Structure from SQL Code and Identify Statement Types?

SQL code analysis in C language

Question:

Can you recommend a freely available parser that can parse SQL code and generate a tree structure? Furthermore, can this parser identify the type of statement represented by each node in the tree? For example, if a node contains a loop condition, it should be designated as a "loop type" node.

Answer:

Of course! For Transact-SQL (specifically Microsoft SQL Server) you can take advantage of the Microsoft.SqlServer.Management.SqlParser.Parser namespace. This is included in the Microsoft.SqlServer.Management.SqlParser.dll assembly, which is included with SQL Server and is freely distributed.

Here is an example method you can use to parse T-SQL as a string into a sequence of tokens:

IEnumerable<tokeninfo> ParseSql(string sql)
{
    ParseOptions parseOptions = new ParseOptions();
    Scanner scanner = new Scanner(parseOptions);

    int state = 0,
        start,
        end,
        lastTokenEnd = -1,
        token;

    bool isPairMatch, isExecAutoParamHelp;

    List<tokeninfo> tokens = new List<tokeninfo>();

    scanner.SetSource(sql, 0);

    while ((token = scanner.GetNext(ref state, out start, out end, out isPairMatch, out isExecAutoParamHelp)) != (int)Tokens.EOF)
    {
        TokenInfo tokenInfo =
            new TokenInfo()
            {
                Start = start,
                End = end,
                IsPairMatch = isPairMatch,
                IsExecAutoParamHelp = isExecAutoParamHelp,
                Sql = sql.Substring(start, end - start + 1),
                Token = (Tokens)token,
            };

        tokens.Add(tokenInfo);

        lastTokenEnd = end;
    }

    return tokens;
}

The

TokenInfo class is a simple class with the properties mentioned in the methods. Tokens is an enumeration containing constants like TOKEN_BEGIN, TOKEN_COMMIT and TOKEN_EXISTS.

Note: This namespace is now available as a separate NuGet package at: https://www.php.cn/link/e6e8bbe351bf19f963820a96543f25db.

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