Firebird 2.5.2更改Blob子类型 [英] Firebird 2.5.2 change blob subtype

问题描述

是否可以更改BLOB字段的SUBTYPE?

Is there a posibility to change the SUBTYPE of a BLOB field ?

我有一个带有SUBTYPE BINARY的BLOB，需要将其更改为SUBTYPE TEXT，因为我在BLOB中有一些奇怪的字符，而在带有SUBTYPE TEXT的BLOB中我没有这个问题

I have a BLOB with SUBTYPE BINARY an need to change it to SUBTYPE TEXT, because i get some strange Characters into the BLOB and in a BLOB with SUBTYPE TEXT i don't have this Problem

推荐答案

无法直接更改Blob列的子类型(尝试这样做将产生错误无法更改BLOBCOLUMN列的数据类型.BLOB或ARRAY列不支持更改数据类型." )

Directly altering the subtype of a blob column is not possible (attempts to do this will give the error "Cannot change datatype for column BLOBCOLUMN. Changing datatype is not supported for BLOB or ARRAY columns.")

您将需要

1. 添加一个带有明确字符集的新列(我根据您的评论假设Windows 1252)

1. Add a new column with an explicit character set (I am assuming windows 1252 based on your comments)

ALTER TABLE table_name
  ADD blobcolumn_new BLOB SUB_TYPE TEXT CHARACTER SET WIN1252

将数据从旧列复制到新列:

Copy the data from the old column to the new column:

UPDATE table_name SET blobcolumn_new = blobcolumn

删除旧列

Drop the old column

ALTER TABLE table_name
  DROP blobcolumn

重命名新列

Rename the new column

ALTER TABLE table_name
  ALTER COLUMN blobcolumn_new TO blobcolumn

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