从 C# 中的字符串中提取特定单词

Question

Although its easy in pyhton but i am new to C# and i am having trouble extracting a particular word from a string. i have two txt file.

abc.txt

select * from schema1.table1

xyz.txt

select * from schema2.table2 where a=5

i need to extract " schema1 " and " schema2 " words only but i tried but i am having trouble with it as it is C#.

MY code

            {
                StreamReader sr = new StreamReader(file);
                string data = sr.ReadLine();
                while (data != null)
                {
                string[] values = data.Split('.');
                foreach (string value in values)
                   {
                    Console.WriteLine(value.Split(' ').Last());
                    data = sr.ReadLine();
                   }
                }
            }

but the output gives whole lot of other words too. any kind of lead is appreciated.

Answer 1

You may try the following:

string sql = "select * from schema2.table2 where a=5";
var schema = Regex.Replace(sql, @"^select \* from ([^.]+)\.\S+.*$", "$1");
Console.WriteLine(schema);  // schema2

This answer makes very large assumptions, including that every SQL query you would need to parse would always start with select * from some_schema.some_table . Obviously, for more complex/different queries, the above logic would fail.

In general, you might need to find a .NET library which can parse SQL queries.