The next table shows the extended data type combinations that you can cast.
| Target Type | Opaque Type | Distinct Type | Named ROW Type | Unnamed ROW Type | Collection Type | Built-in Type |
|---|---|---|---|---|---|---|
| Opaque Type | Explicit or implicit | Explicit | Explicit | Not Allowed | Not Allowed | Explicit or implicit3 |
| Distinct Type | Explicit3 | Explicit | Explicit | Not Allowed | Not Allowed | Explicit or implicit |
| Named ROW Type | Explicit3 | Explicit | Explicit3 | Explicit1 | Not Allowed | Not Allowed |
| Unnamed ROW Type | Not Allowed | Not Allowed | Explicit1 | Implicit1 | Not Allowed | Not Allowed |
| Collection Type | Not Allowed | Not Allowed | Not Allowed | Not Allowed | Explicit2 | Not Allowed |
| Built-in Type | Explicit or implicit3 | Explicit or implicit | Not Allowed | Not Allowed | Not Allowed | System defined (implicit) |
| 1 Applies when two ROW types are structurally equivalent or casts exist to handle data conversions where corresponding field types are not the same.2 Applies when a cast exists to convert between the element types of the respective collection types.3 Applies when a user-defined cast exists to convert between the two data types. | ||||||
The table shows only whether or not a cast between a source type and a target type are possible. In some cases, you must first create a user-defined cast before you can perform a conversion between two data types. In other cases, the database server provides either an implicit cast or a built-in cast that you must explicitly invoke.
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