将NTEXT和nvarchar（255）转换为nvarchar（max）的问题

Question

How can I convert an NTEXT column to NVARCHAR(MAX)?

I have 4 databases in which there is a table that exists in all four. Inside of this table there exists a Notes column of type NTEXT except in one database where that column is nvarchar(255) .

So:

• 3 NTEXT
• 1 nvarchar(255)

My ETL takes data from these four tables and puts them into one table where the Notes column is of type nvarchar(max) .

I didn't realize that one column was nvarchar(255) until my ETL didn't work because all four tables are supposed to be identical in structure.

Error:

[Source DB [25]] Error: There was an error with Source DB.Outputs[OLE DB Source Output].Columns[Notes] on Source DB.Outputs[OLE DB Source Output]. The column status returned was: "DBSTATUS_UNAVAILABLE".

I'm guessing this is the issue since the error wasn't specific. How can I convert this column to nvarchar(max) ?

Answer 1

在oledb源代码中，从表中写入一个select并将列转换为NTEXT，即

SELECT ..., Convert(ntext, Notes) as Notes