Batch multiple select statements when calling Oracle from ADO.NET

Question

I want to batch multiple select statements to reduce round trips to the database. The code looks something like the pseudo code below. It works perfectly on SQL Server, but

Answer 1

How about:

var sql = @"
            select * from table1 UNION
            select * from table2 UNION
            select * from table3";

Answer 2

You should write an anonymous pl/sql block that returns 3 ref cursors.

edit1: Here it is done in an anonymous pl/sql block with one cursor. It should work with three too. Oracle ref cursors don't lock data and they are the fastest way to return a result set from a pl/sql procedure or an anonymous pl/sql bloc.

http://www.oracle.com/technetwork/issue-archive/2006/06-jan/o16odpnet-087852.html

Answer 3

An example in C# with multiple cursors and an input parameter:

string ConnectionString = "connectionString";
OracleConnection conn = new OracleConnection(ConnectionString);
StringBuilder sql = new StringBuilder();

sql.Append("begin ");
sql.Append("open :1 for select * from table_1 where id = :id; ");
sql.Append("open :2 for select * from table_2; ");
sql.Append("open :3 for select * from table_3; ");
sql.Append("end;");

OracleCommand comm = new OracleCommand(sql.ToString(),_conn);

comm.Parameters.Add("p_cursor_1", OracleDbType.RefCursor, DBNull.Value, ParameterDirection.Output);

comm.Parameters.Add("p_id", OracleDbType.Int32, Id, ParameterDirection.Input);

comm.Parameters.Add("p_cursor_2", OracleDbType.RefCursor, DBNull.Value, ParameterDirection.Output);

comm.Parameters.Add("p_cursor_3", OracleDbType.RefCursor, DBNull.Value, ParameterDirection.Output);

conn.Open();

OracleDataReader dr = comm.ExecuteReader();

Answer 4

why not use stored procedures instead?

But, if you want to batch them in an inline query, you can use a semicolon (;) to seperate the statements.

var sql = @"BEGIN
                select * from table1;
                select * from table2;
                select * from table3;
            END;";

EDIT: You take a look at this SO question.

EDIT2: Take a look at this answer.