"The text, ntext, and image data types cannot be compared or sorted, …"

When reading separate columns using the following DB structure and code, I get error when the column is of the type TEXT.

The table schema type for that is:

TABLE_NAME            COLUMN_NAME        DATA_TYPE      CHARACTER_MAXIMUM_LENGTH
----------            -----------        ---------      ------------------------
mytable  col_name  text  2147483647

I’m then trying to reading all the columns (one at a time) using:

def get_data(table_list):
    cursor = connect()
    for table, column in table_list:
        SQLA = 'SELECT TOP 1 [{}] as data FROM [{}] ORDER BY [{}] DESC;'.format(column, table, column)
        cursor.execute(SQLA)
        
        while 1:
            row = cursor.fetchone()
            if not row:
                break
            print(' Data : {}'.format(row.data))
    db_close(cursor)

This works fine until it hits the first column with a TEXT type (as shown above).

Running the same query from powershell CMD yields the same result:

$ iex "$qcmd 'SELECT TOP 1 [notes] FROM [mytable ] ORDER BY [notes] DESC;' -W"

Msg 306, Level 16, State 2, Server DBSQL01, Line 1
The text, ntext, and image data types cannot be compared or sorted, except when using IS NULL or LIKE operator.

---

Environment

[INFO]  Getting MS SQL Server Version info...
 ------------------------------------------------------------
 Microsoft SQL Server 2008 R2 (SP3-GDR) (KB4057113) - 10.50.6560.0 (X64)
 Dec 28 2017 15:03:48
 Copyright (c) Microsoft Corporation
 Enterprise Edition (64-bit) on Windows NT 6.2 <X64> (Build 9200: ) (Hypervisor)

• pyodbc 4.0.32
• Python: 3.10.3

Issue

Observed behavior:

I get the following error trying to read MS SQL columns of the type TEXT.

pyodbc.ProgrammingError: ('42000', '[42000] [Microsoft][ODBC Driver 17 for SQL Server][SQL Server]
The text, ntext, and image data types cannot be compared or sorted, except when using IS NULL or LIKE operator. (306) (SQLExecDirectW)')

Expected behavior:

That it works without errors.

[v-chojas]

Yes, ntext is UTF-16 and image is plain binary. You can cast them to nvarchar(max) and varbinary(max) respectively.

[v-chojas]

You can try cast(col_name as varchar(max))

The text type is one of the early large object (LOB) types, it is stored and processed differently by the server than the regular types.