If I may suggest...

If this is just for experimentation, that's fine. If this is a design for an app, just don't do this. You're opening yourself to all sorts of complexities, SQL Injection being just one.

As for how you do this:

DECLARE @sSQL NVARCHAR(4000)

SELECT @sSQL = t_sql from t_test WHERE -- whatever condition to get the row you want.

EXEC (@sSQL)

Again, DO NOT go this route/design for a real application.