sql: clarify unsupported behavior in generated column (#2000)

pingcap · Mar 11, 2020 · 2ef7942 · 2ef7942
1 parent d0c07fd
commit 2ef7942
Showing 1 changed file with 3 additions and 0 deletions.
diff --git a/reference/sql/generated-columns.md b/reference/sql/generated-columns.md
@@ -85,4 +85,7 @@ The current limitations of JSON and generated columns are as follows:
 
 - You cannot add the generated column in the storage type of `STORED` through `ALTER TABLE`.
 - You cannot create an index on the generated column through `ALTER TABLE`.
+- You can neither convert a generated stored column to a normal column through the `ALTER TABLE` statement nor convert a normal column to a generated stored column.
+- You cannot modify the **expression** of a generated stored column through the `ALTER TABLE` statement.
+- You cannot assign the `DEFAULT` value to generated columns in DML statements.
 - Not all [JSON functions](/reference/sql/functions-and-operators/json-functions.md) are supported.