How to get table name from string that contain SELECT statement

Question

i have a string that contain a sql command,

something like this:

strCommand = "Select [Feild1], [Feild2] From TableName Order By [Feild1] desc" ;

How can find table name in this string?

Answer 1

The solutions so far have all gone with the searching within strings approach. You've not mentioned if your SQL queries will always look similar, but there are many variants of a query to include which these solutions will break on. Consider...

• SELECT Field1, Field2 FROM TableName
• SELECT Field1, Field2 FROM [TableName]
• SELECT Field1, Field2 FROM dbo.TableName
• SELECT Field1, Field2 FROM Table1Name, Table2Name

If the query you're trying to parse is one you have the database for, you can get SQL server to do the hard work of parsing the query for you, instead of trying to account for all the cases in SQL. You can execute a query using SET SHOWPLAN_ALL ON, which will produce a table of the query plan. You can then analyse the Arguments column, which contains all of the fields the query will involve in a standard format. An example program is below:

SqlConnection conn = new SqlConnection(CONNECTIONSTRING);
conn.Open();

SqlCommand cmd = conn.CreateCommand();
cmd.CommandText = "SET SHOWPLAN_ALL ON";
cmd.ExecuteNonQuery();
cmd.CommandText = "SELECT [Field1], [Field2] FROM [TableName]";

DataTable dt = new DataTable();
dt.Load(cmd.ExecuteReader());

Regex objectRegex = new Regex(@"^OBJECT:\(\[(?<database>[^\]]+)\]\.\[(?<schema>[^\]]+)\]\.\[(?<table>[^\]]+)\]\.\[(?<field>[^\]]+)\]\)$", RegexOptions.ExplicitCapture);

List<string> lstTables = new List<string>();
foreach (DataRow row in dt.Rows)
{
    string argument = row["Argument"].ToString();
    if (!String.IsNullOrEmpty(argument))
    {
        Match m = objectRegex.Match(argument);
        if (m.Success)
        {
            string table = m.Groups["schema"] + "." + m.Groups["table"];
            if (!lstTables.Contains(table))
            {
                lstTables.Add(table);
            }
        }
    }
}

Console.WriteLine("Query uses the following tables: " + String.Join(", ", lstTables));

This will deal with all forms of query name and return all tables which are involved in the query, no matter how they are included.