From 6e3e08b13a8d35ced4bcbeb9c8611677f50b1e49 Mon Sep 17 00:00:00 2001 From: deardrops Date: Wed, 11 Mar 2020 20:44:42 +0800 Subject: [PATCH] sql: clarify unsupported behavior in generated column --- reference/sql/generated-columns.md | 3 +++ 1 file changed, 3 insertions(+) diff --git a/reference/sql/generated-columns.md b/reference/sql/generated-columns.md index c578460bc1969..43ba05439bdc5 100644 --- 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.