ddl2cpp command line argument for custom types

README.md

@@ -239,12 +239,46 @@ Create headers for them with provided Python script:
 ```
 %sqlpp11_dir%/scripts/ddl2cpp ~/temp/MyTable.ddl  ~/temp/MyTable %DatabaseNamespaceForExample%
 ```
-(In case you’re getting notes about unsupported column type take a look at the other datatypes in sqlpp11/data_types. They are not hard to implement.)
+
+In case you’re getting notes about unsupported column type consider:
+  - Take a look at the other datatypes in sqlpp11/data_types. They are not hard to implement.
+  - Use the `--datatype-file` command line argument as described below.
 
 Include generated header (MyTable.h), that’s all.
 
 If you prefer Ruby over Python, you might want to take a look at https://github.com/douyw/sqlpp11gen
 
+Unsupported column types:
+-------------
+__Map unsupported column types to supported column types with a csv file__:
+
+One can use the `--datatype-file` command line argument for the ddl2cpp script to map unsupported column types to supported column types.
+
+The format of the csv file is:
+```
+<dataType>, <col_type1>, <col_type2>
+<dataType>, <col_type3>
+```
+
+Where `<dataType>` is one or more of the following internal types:
+
+  - `Boolean`
+  - `Integer`
+  - `Serial`
+  - `FloatingPoint`
+  - `Text`
+  - `Blob`
+  - `Date`
+  - `DateTime`
+  - `Time`
+
+Example:
+
+```
+Boolean, one_or_zero
+Text, url, uuid
+```
+
 Contact:
 --------
   * Issues at https://github.com/rbock/sqlpp11/issues