postgresql - 在 PostgreSQL-11 中有条件地更新字段时出错

Question

给定以下查询:

insert into shopify_app_shops as s
    (
        myshopify_name,
        hostname,
        user_status,
        offline_access_token,
        offline_access_token_updated_at,
        updated_at
    )
    values
    (
        %(myshopify_name)s,
        %(hostname)s,
        %(user_status)s,
        %(offline_access_token)s,
        now(),
        now()
    )
    on conflict (myshopify_name)
    do update
        set
            hostname=%(hostname)s,
            user_status=%(user_status)s,
            offline_access_token_updated_at =
            CASE
                WHEN offline_access_token == %(offline_access_token)s
                THEN offline_access_token_updated_at
                ELSE now()
            END,
            offline_access_token=%(offline_access_token)s,
            updated_at = now()
            returning myshopify_name
            ;

我得到错误:

Failed with: column reference "offline_access_token" is ambiguous LINE 28: WHEN offline_access_token == NULL

但是，如果我通过像这样在表名前添加来完全指定字段:

WHEN shopify_app_shops.offline_access_token == %(offline_access_token)s

我反而得到这个错误:

Failed with: invalid reference to FROM-clause entry for table "shopify_app_shops" LINE 28: WHEN shopify_app_shops.offline_access_token == NULL

此时我不知所措!

documentation for postgresql-11 update statements明确指出用于设置值的表达式可以包含对其他字段的引用以访问旧值:

expression

An expression to assign to the column. The expression can use the old values of this and other columns in the table.

那我做错了什么？

Answer 1

使用表别名

WHEN s.offline_access_token ...

使用别名时表名不可见。不相关，您可能应该使用 IS NOT DISTINCT FROM而不是 ==。