Question

I have this code in MS SQL:

select * from table where column1 in (select column2 from table)

How can I translate this using a DataTable?

Something along the lines of: table.select("column1 in column2")

Answer 1

you can’t.
but you can do it via linq + table.select:

table.Select(string.Format("CITY in '{0}'",string.Join("','",table.Rows.OfType<DataRow>().Select(r=>r["COUNTRY"].ToString()).Distinct())))

EXPLANATION:
suppose you have a very simple table

ID CITY COUNTRY
1 NY USA
2 Moscow Russia
3 LA USA
4 St Peterburg Russia

1. Using LINQ to Objects we select all unique values from Country column and concatenate values (via string.Join) to the IN filter statement string. For our example it will be USA’,’Russia
2. surround IN filter statement with quotes via string.Format: ‘USA’,’Russia’
3. Pass IN filter in dataTable.Select(“CITY IN (‘USA’,’Russia’)”)

FYI:

If you need to execute really cool SQL queries against DataTables\DataSets you can use NQuery it is very fast and standards compliant.