Add small remark to docstring.

Author: evetion

src/tables.jl

@@ -150,6 +150,7 @@ The resultset iterator supports the [Tables.jl](https://github.com/JuliaData/Tab
 like `DataFrame(results)`, `CSV.write("results.csv", results)`, etc.
 
 Passing `strict=true` to `DBInterface.execute` will cause the resultset iterator to return values of the exact type specified by SQLite.
+While more type-stable, determining the exact types of the results can be more expensive as it will iterate through each column to find the first non-NULL value to determine the type.
 """
 function DBInterface.execute(
     stmt::Stmt,