Merge pull request #4222 from soerenwolfers/patch-63

Update typecasting.md

docs/sql/data_types/typecasting.md

@@ -12,11 +12,17 @@ Explicit typecasting is performed by using a `CAST` expression. For example, `CA
 
 ## Implicit Casting
 
-In many situations, the system will add casts by itself. This is called *implicit* casting. This happens for example when a function is called with an argument that does not match the type of the function, but can be casted to the desired type.
+In many situations, the system will add casts by itself. This is called *implicit* casting and happens, for example, when a function is called with an argument that does not match the type of the function but can be casted to the required type.
+
+Implicit casts can only be added for a number of type combinations, and is generally only possible when the cast cannot fail. For example, an implicit cast can be added from `INTEGER` to `DOUBLE` – but not from `DOUBLE` to `INTEGER`.
 
 Consider the function `sin(DOUBLE)`. This function takes as input argument a column of type `DOUBLE`, however, it can be called with an integer as well: `sin(1)`. The integer is converted into a double before being passed to the `sin` function.
 
-Implicit casts can only be added for a number of type combinations, and is generally only possible when the cast cannot fail. For example, an implicit cast can be added from `INTEGER` to `DOUBLE` – but not from `DOUBLE` to `INTEGER`.
+### Combination casting
+
+When values of different types need to be combined to an unspecified joint parent type, the system will perform implicit casts to an automatically selected parent type. For example, `list_value(1::INT64, 1::UINT64)` creates a list of type `INT128[]`. The implicit casts performed in this situation are sometimes more lenient than regular implicit casts. For example, a `BOOL` value may be cast to `INT` (with `true` mapping to `1` and `false` to `0`) even though this is not possible for regular implicit casts.
+
+This *combination casting* occurs for comparisons (`==` / `<` / `>`), set operations (`UNION` / `EXCEPT` / `INTERSECT`), and nested type constructors (`list_value` / `[...]` / `MAP`).
 
 ## Casting Operations Matrix