[英]change the type of column in postgres not working
I have a column of type object, and i need to make it from another object type, (the table is empty )我有一列对象类型,我需要从另一个对象类型中创建它,(表是空的)
i tried to do :我试着做:
ALTER TABLE invoice_history ALTER COLUMN invoice_info TYPE invoice USING (trim(invoice_info)::invoice);
ERROR: function pg_catalog.btrim(invoice_item) does not exist LINE 1: ...ory ALTER COLUMN invoice_info TYPE invoice USING (trim(invoi... ^ HINT: No function matches the given name and argument types. You might need to add explicit type casts.错误:函数 pg_catalog.btrim(invoice_item) 不存在第 1 行:...ory ALTER COLUMN invoice_info TYPE invoice USING (trim(invoi... ^ 提示:没有函数匹配给定的名称和参数类型。您可能需要添加显式类型转换。
and :和 :
ALTER TABLE invoice_history
ALTER COLUMN invoice_info TYPE invoice USING (invoice_info::invoice)
given this error :鉴于此错误:
ERROR: cannot cast type invoice_item to invoice LINE 2: ...UMN invoice_info TYPE invoice USING (invoice_info::invoice...错误:无法将类型 invoice_item 转换为发票第 2 行:...UMN invoice_info TYPE invoice USING (invoice_info::invoice...
what i should do ?我该做什么 ? and how can it changed ?它怎么能改变?
If the table is empty (or you do not care about the column value conversion) use just null
, eg:如果表为空(或者您不关心列值转换),请仅使用null
,例如:
alter table invoice_history
alter invoice_info type invoice using null;
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