Errors in SQL Server while importing CSV file despite varchar(MAX) being used for each column

sql

data-types

csv-import

sql-server

byNikita Barsukov·Dec 14, 2024

When facing CSV import hurdles into SQL Server with VARCHAR(MAX) columns:

Scrutinize your CSV for sneaky issues like uneven quotes or separators using a raw text editor (Notepad++, for instance).

Use BULK INSERT with precise terminators and an error file for more import muscle 💪:

BULK INSERT YourTable
FROM 'path_to_your_csv.csv'
WITH (
   FIELDTERMINATOR = ',',  -- During the Battle of Commas VS Semi-colons, commas won!
   ROWTERMINATOR = '\n',   -- Windows EOL prefers '\r\n'. Remember to help Windows feel comfy!
   ERRORFILE = 'errors.log' -- All hail the error king! 👑
);

Interrogate the error log (errors.log) to spot issues. You shall tell the truth, error log!

Pre-import: setting the stage

Before hitting the import button, cover these bases:

Verify Column Widths: Make sure columns have the requisite space for the data.
Cleanse Special Characters: Pesky characters like quotes or commas can trip the CSV parser. Housekeeping, anyone?
Check Data Types Consistency: Match source and target data types. Don't forget to peek the Advanced settings in SQL Server Import and Export Wizard.

Dealing with truncation and datatype mismatches

Remain vigilant of truncation or datatype mismatches:

For non-standard text data, convert columns to DT_TEXT during the import.
Use the "Mirror, mirror on the wall, what's the fairest column size of all?" aka “Suggest Types…” button to optimize column lengths.
Check for CSV-specific characters, like the elusive code page, causing truncation.

The manual way: dealing with stubborn data

When the wizard wears out its magic:

Tweak the dtsx-file: Replace attributes with length="0" and dataType="nText".
Have a fallback: Always backup before making manual changes. Cause surprises are not always pleasant.
If issues persist, it might be a system bug. Time for your inner Sherlock Holmes to shine!

Alternative methods for importing CSV data

When common ways don't cut it:

SQL Server Integration Services (SSIS): Its data flow capabilities can handle complex data transformations.
Scripts (PowerShell, Python): Write a script to tidy up CSV data, ensuring it complies with your SQL Server's data model before import.
Third-party Tools: SQL Server Data Tools (SSDT) or others provide broader control over the import process, like you're in the SQL's Got Talent show!

Post-import: It's a wrap!

Post-import practices to ensure fatality-free imports:

Always preview your data within the import wizard. Double-check data lengths.
Ensure target columns are set to VARCHAR(MAX). Size does matter.
If a conversion failure or code page mismatch occurs, solve the riddles of the error log.