diff --git a/src/types/column/concat.rs b/src/types/column/concat.rs
index 6fae8d09..3a774be3 100644
--- a/src/types/column/concat.rs
+++ b/src/types/column/concat.rs
@@ -2,6 +2,7 @@ use std::iter;
 
 use crate::{
     binary::Encoder,
+    errors::{Result, Error, FromSqlError},
     types::{SqlType, Value, ValueRef},
 };
 
@@ -64,6 +65,15 @@ impl ColumnData for ConcatColumnData {
     fn clone_instance(&self) -> BoxColumnData {
         unimplemented!()
     }
+
+    unsafe fn get_internal(&self, pointers: &[*mut *const u8], level: u8) -> Result<()> {
+        if level == 0xff {
+            *pointers[0] = &self.data as *const Vec<ArcColumnData> as *mut u8;
+            Ok(())
+        } else {
+            Err(Error::FromSql(FromSqlError::UnsupportedOperation))
+        }
+    }
 }
 
 fn build_index<'a, I>(sizes: I) -> Vec<usize>
diff --git a/src/types/column/iter.rs b/src/types/column/iter/mod.rs
similarity index 86%
rename from src/types/column/iter.rs
rename to src/types/column/iter/mod.rs
index 98612fb5..29156dcf 100644
--- a/src/types/column/iter.rs
+++ b/src/types/column/iter/mod.rs
@@ -12,13 +12,17 @@ use chrono_tz::Tz;
 
 use crate::{
     errors::{Error, FromSqlError, Result},
-    types::{column::StringPool, decimal::NoBits, Column, Decimal, Simple, SqlType},
+    types::{
+        column::{column_data::ArcColumnData, StringPool},
+        decimal::NoBits,
+        Column, ColumnType, Complex, Decimal, Simple, SqlType,
+    },
 };
 
 macro_rules! simple_num_iterable {
     ( $($t:ty: $k:ident),* ) => {
         $(
-            impl<'a> SimpleIterable<'a> for $t {
+            impl<'a> Iterable<'a, Simple> for $t {
                 type Iter = slice::Iter<'a, $t>;
 
                 fn iter(column: &'a Column<Simple>, column_type: SqlType) -> Result<Self::Iter> {
@@ -112,10 +116,10 @@ macro_rules! exact_size_iterator {
     };
 }
 
-pub trait SimpleIterable<'a> {
-    type Iter: Iterator + 'a;
+pub trait Iterable<'a, K: ColumnType> {
+    type Iter: Iterator;
 
-    fn iter(column: &'a Column<Simple>, column_type: SqlType) -> Result<Self::Iter>;
+    fn iter(column: &'a Column<K>, column_type: SqlType) -> Result<Self::Iter>;
 }
 
 enum StringInnerIterator<'a> {
@@ -384,8 +388,6 @@ impl<'a> ExactSizeIterator for UuidIterator<'a> {
     }
 }
 
-
-
 impl<'a> DateIterator<'a> {
     #[inline(always)]
     unsafe fn next_unchecked(&mut self) -> Date<Tz> {
@@ -519,7 +521,7 @@ impl<'a, I: Iterator> Iterator for ArrayIterator<'a, I> {
 
 impl<'a, I: Iterator> FusedIterator for ArrayIterator<'a, I> {}
 
-impl<'a> SimpleIterable<'a> for Ipv4Addr {
+impl<'a> Iterable<'a, Simple> for Ipv4Addr {
     type Iter = Ipv4Iterator<'a>;
 
     fn iter(column: &'a Column<Simple>, _column_type: SqlType) -> Result<Self::Iter> {
@@ -540,8 +542,7 @@ impl<'a> SimpleIterable<'a> for Ipv4Addr {
     }
 }
 
-
-impl<'a> SimpleIterable<'a> for Ipv6Addr {
+impl<'a> Iterable<'a, Simple> for Ipv6Addr {
     type Iter = Ipv6Iterator<'a>;
 
     fn iter(column: &'a Column<Simple>, _column_type: SqlType) -> Result<Self::Iter> {
@@ -562,7 +563,7 @@ impl<'a> SimpleIterable<'a> for Ipv6Addr {
     }
 }
 
-impl<'a> SimpleIterable<'a> for uuid::Uuid {
+impl<'a> Iterable<'a, Simple> for uuid::Uuid {
     type Iter = UuidIterator<'a>;
 
     fn iter(column: &'a Column<Simple>, _column_type: SqlType) -> Result<Self::Iter> {
@@ -583,7 +584,7 @@ impl<'a> SimpleIterable<'a> for uuid::Uuid {
     }
 }
 
-impl<'a> SimpleIterable<'a> for &[u8] {
+impl<'a> Iterable<'a, Simple> for &[u8] {
     type Iter = StringIterator<'a>;
 
     fn iter(column: &'a Column<Simple>, column_type: SqlType) -> Result<Self::Iter> {
@@ -630,7 +631,7 @@ impl<'a> SimpleIterable<'a> for &[u8] {
     }
 }
 
-impl<'a> SimpleIterable<'a> for Decimal {
+impl<'a> Iterable<'a, Simple> for Decimal {
     type Iter = DecimalIterator<'a>;
 
     fn iter(column: &'a Column<Simple>, column_type: SqlType) -> Result<Self::Iter> {
@@ -677,7 +678,7 @@ impl<'a> SimpleIterable<'a> for Decimal {
     }
 }
 
-impl<'a> SimpleIterable<'a> for DateTime<Tz> {
+impl<'a> Iterable<'a, Simple> for DateTime<Tz> {
     type Iter = DateTimeIterator<'a>;
 
     fn iter(column: &'a Column<Simple>, column_type: SqlType) -> Result<Self::Iter> {
@@ -691,7 +692,7 @@ impl<'a> SimpleIterable<'a> for DateTime<Tz> {
     }
 }
 
-impl<'a> SimpleIterable<'a> for Date<Tz> {
+impl<'a> Iterable<'a, Simple> for Date<Tz> {
     type Iter = DateIterator<'a>;
 
     fn iter(column: &'a Column<Simple>, column_type: SqlType) -> Result<Self::Iter> {
@@ -738,9 +739,9 @@ fn date_iter<T>(
     Ok((ptr, end, *tz))
 }
 
-impl<'a, T> SimpleIterable<'a> for Option<T>
+impl<'a, T> Iterable<'a, Simple> for Option<T>
 where
-    T: SimpleIterable<'a>,
+    T: Iterable<'a, Simple>,
 {
     type Iter = NullableIterator<'a, T::Iter>;
 
@@ -775,9 +776,9 @@ where
     }
 }
 
-impl<'a, T> SimpleIterable<'a> for Vec<T>
+impl<'a, T> Iterable<'a, Simple> for Vec<T>
 where
-    T: SimpleIterable<'a>,
+    T: Iterable<'a, Simple>,
 {
     type Iter = ArrayIterator<'a, T::Iter>;
 
@@ -810,3 +811,104 @@ where
         })
     }
 }
+
+pub struct ComplexIterator<'a, T>
+where
+    T: Iterable<'a, Simple>,
+{
+    column_type: SqlType,
+
+    data: &'a Vec<ArcColumnData>,
+
+    current_index: usize,
+    current: Option<<T as Iterable<'a, Simple>>::Iter>,
+
+    _marker: marker::PhantomData<T>,
+}
+
+impl<'a, T> Iterator for ComplexIterator<'a, T>
+where
+    T: Iterable<'a, Simple>,
+{
+    type Item = <<T as Iterable<'a, Simple>>::Iter as Iterator>::Item;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.current_index == self.data.len() && self.current.is_none() {
+            return None;
+        }
+
+        if self.current.is_none() {
+            let column: Column<Simple> = Column {
+                name: String::new(),
+                data: self.data[self.current_index].clone(),
+                _marker: marker::PhantomData,
+            };
+
+            let iter = unsafe { T::iter(mem::transmute(&column), self.column_type) }.unwrap();
+
+            self.current = Some(iter);
+            self.current_index += 1;
+        }
+
+        let ret = match self.current {
+            None => None,
+            Some(ref mut iter) => iter.next(),
+        };
+
+        match ret {
+            None => {
+                self.current = None;
+                self.next()
+            }
+            Some(r) => Some(r),
+        }
+    }
+}
+
+impl<'a, T> Iterable<'a, Complex> for T
+where
+    T: Iterable<'a, Simple> + 'a,
+{
+    type Iter = ComplexIterator<'a, T>;
+
+    fn iter(column: &Column<Complex>, column_type: SqlType) -> Result<Self::Iter> {
+        let data: &Vec<ArcColumnData> = unsafe {
+            let mut data: *const Vec<ArcColumnData> = ptr::null();
+
+            column.get_internal(
+                &[&mut data as *mut *const Vec<ArcColumnData> as *mut *const u8],
+                0xff,
+            )?;
+
+            &*data
+        };
+
+        Ok(ComplexIterator {
+            column_type,
+            data,
+
+            current_index: 0,
+            current: None,
+
+            _marker: marker::PhantomData,
+        })
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::types::Block;
+
+    #[test]
+    fn test_complex_iter() {
+        let lo = Block::new().column("?", vec![1_u32, 2]);
+        let hi = Block::new().column("?", vec![3_u32, 4, 5]);
+
+        let block = Block::concat(&[lo, hi]);
+
+        let columns = block.columns()[0].iter::<u32>().unwrap();
+        let actual: Vec<_> = columns.collect();
+
+        assert_eq!(actual, vec![&1_u32, &2, &3, &4, &5])
+    }
+}
diff --git a/src/types/column/mod.rs b/src/types/column/mod.rs
index c2cc5852..62569cc2 100644
--- a/src/types/column/mod.rs
+++ b/src/types/column/mod.rs
@@ -11,13 +11,13 @@ use crate::{
     binary::{Encoder, ReadEx},
     errors::{Error, FromSqlError, Result},
     types::{
-        column::iter::SimpleIterable,
         column::{
             column_data::ArcColumnData,
             decimal::{DecimalAdapter, NullableDecimalAdapter},
             fixed_string::{FixedStringAdapter, NullableFixedStringAdapter},
             ip::{Ipv6, IpColumnData, Ipv4},
             string::StringAdapter,
+            iter::Iterable,
         },
         decimal::NoBits,
         SqlType, Value, ValueRef,
@@ -37,7 +37,7 @@ mod decimal;
 mod factory;
 pub(crate) mod fixed_string;
 mod ip;
-mod iter;
+pub(crate) mod iter;
 mod list;
 mod nullable;
 mod numeric;
@@ -139,7 +139,9 @@ impl Column<Simple> {
             }
         }
     }
+}
 
+impl<K: ColumnType> Column<K> {
     /// Returns an iterator over the column.
     ///
     /// ### Example
@@ -154,7 +156,7 @@ impl Column<Simple> {
     /// #     let pool = Pool::new(database_url);
     /// #     let mut client = pool.get_handle().await?;
     ///       let mut stream = client
-    ///             .query("SELECT number as n1, number as n2, number as n3 FROM numbers(10000000)")
+    ///             .query("SELECT number as n1, number as n2, number as n3 FROM numbers(100000000)")
     ///             .stream_blocks();
     ///
     ///       let mut sum = 0;
@@ -175,11 +177,8 @@ impl Column<Simple> {
     /// # });
     /// # ret.unwrap()
     /// ```
-    pub fn iter<'a, T>(&'a self) -> Result<T::Iter>
-    where
-        T: SimpleIterable<'a>,
-    {
-        T::iter(self, self.sql_type())
+    pub fn iter<'a, T: Iterable<'a, K>>(&'a self) -> Result<T::Iter> {
+        <T as Iterable<'a, K>>::iter(self, self.sql_type())
     }
 }