Handling load errors in Snowflake - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a common cause of load errors in Snowflake?

Load errors often happen because of data format issues, like wrong file structure or unexpected characters.

beginner

How does Snowflake help identify load errors?

Snowflake provides error tables and detailed error messages that show which rows failed and why.

intermediate

What is the role of the 'VALIDATION_MODE' option in Snowflake data loading?

It lets you check data for errors without actually loading it, so you can fix problems before the real load.

intermediate

Why use the 'ON_ERROR' parameter during data loading in Snowflake?

It controls what happens when errors occur, like skipping bad rows or stopping the load to fix issues.

advanced

How can you automate handling load errors in Snowflake?

By using error tables and scripts to review and fix errors, then reload only the problematic data.

What does Snowflake do when you set ON_ERROR='SKIP_FILE' during a load?

A Skips the entire file if an error occurs

B Stops loading and reports the error

C Loads all data ignoring errors

D Retries loading the file automatically

ON_ERROR='SKIP_FILE' tells Snowflake to skip the whole file if any error is found.

Which Snowflake feature helps you see which rows failed during loading?

A Error tables

B Data masking

C Virtual warehouses

D Streams

Error tables store details about rows that failed to load, helping you find and fix issues.

What does VALIDATION_MODE='RETURN_ERRORS' do?

A Loads data and ignores errors

B Loads data and stops on first error

C Deletes bad data automatically

D Checks data and returns errors without loading

It validates data and returns errors but does not load the data, allowing you to fix problems first.

If you want to load data but skip only bad rows, which ON_ERROR setting should you use?

A SKIP_ROW

B ABORT_STATEMENT

C CONTINUE

D SKIP_FILE

ON_ERROR='CONTINUE' skips only the rows with errors and loads the rest.

What is the best practice after identifying load errors in Snowflake?

A Ignore errors and continue loading

B Fix errors and reload only the bad data

C Delete the whole table and reload

D Load data without validation

Fixing errors and reloading only the problematic data saves time and keeps data clean.

Explain how Snowflake handles load errors and the options available to control error behavior.

Think about how Snowflake lets you see errors and decide what to do with bad data.

Describe a step-by-step approach to manage and fix load errors in Snowflake.

Imagine you are fixing a broken recipe step by step.

Practice

1. What does the ON_ERROR option do when loading data into Snowflake?

easy

A. It controls how Snowflake handles errors during data loading.

B. It encrypts the data before loading.

C. It speeds up the data loading process.

D. It automatically deletes duplicate rows.

Solution

1. Step 1: Understand the purpose of ON_ERROR

   The ON_ERROR option is used to specify how Snowflake should behave when it encounters errors during data loading.

2. Step 2: Identify the correct behavior

   It can skip bad rows, skip files, or stop the load depending on the setting, thus controlling error handling.

3. Final Answer:

   It controls how Snowflake handles errors during data loading. -> Option A

4. Quick Check:

   ON_ERROR controls error handling [OK]

Hint: ON_ERROR sets error handling behavior during load [OK]

Common Mistakes:

• Confusing ON_ERROR with encryption settings
• Thinking ON_ERROR speeds up loading
• Assuming ON_ERROR deletes duplicates

2. Which of the following is the correct syntax to skip bad rows during a Snowflake COPY INTO command?

easy

A. COPY INTO table_name FROM @stage FILE_FORMAT = (TYPE = 'CSV') ON_ERROR = 'ignore_error';

B. COPY INTO table_name FROM @stage FILE_FORMAT = (TYPE = 'CSV') ON_ERROR = 'skip_file';

C. COPY INTO table_name FROM @stage FILE_FORMAT = (TYPE = 'CSV') ON_ERROR = 'abort_load';

D. COPY INTO table_name FROM @stage FILE_FORMAT = (TYPE = 'CSV') ON_ERROR = 'skip_row';

Solution

1. Step 1: Recall valid ON_ERROR options

   Snowflake supports options like 'skip_file', 'skip_row', and 'abort_load' for ON_ERROR.

2. Step 2: Identify option to skip bad rows

   'skip_row' tells Snowflake to skip only the bad rows, not the entire file.

3. Final Answer:

   ON_ERROR = 'skip_row' -> Option D

4. Quick Check:

   Skip bad rows = skip_row [OK]

Hint: Use 'skip_row' to skip bad rows in ON_ERROR [OK]

Common Mistakes:

• Using 'skip_file' to skip rows instead of files
• Using invalid ON_ERROR values like 'ignore_error'
• Confusing 'abort_load' with skipping errors

3. Given this COPY command:

COPY INTO my_table FROM @my_stage FILE_FORMAT = (TYPE = 'CSV') ON_ERROR = 'skip_file';

If one file has 5 bad rows, what happens?

medium

A. The entire file with bad rows is skipped, other files load normally.

B. Only the 5 bad rows are skipped, rest of the file loads.

C. The load stops immediately with an error.

D. All files are skipped regardless of errors.

Solution

1. Step 1: Understand ON_ERROR = 'skip_file'

   This option skips the entire file if any error occurs in it.

2. Step 2: Apply to scenario

   Since one file has 5 bad rows, Snowflake skips that whole file but continues loading other files.

3. Final Answer:

   The entire file with bad rows is skipped, other files load normally. -> Option A

4. Quick Check:

   skip_file skips whole file on error [OK]

Hint: 'skip_file' skips whole file if any error found [OK]

Common Mistakes:

• Thinking only bad rows are skipped with 'skip_file'
• Assuming load stops on first error
• Believing all files skip on one bad file

4. You run a COPY INTO command with ON_ERROR = 'skip_row' but still see the load failing. What is a likely cause?

medium

A. ON_ERROR only works for JSON files, not CSV.

B. The file format is incorrect causing parsing errors.

C. You must set ON_ERROR to 'skip_file' to avoid failures.

D. The target table does not exist.

Solution

1. Step 1: Understand ON_ERROR limitations

   ON_ERROR skips bad rows but cannot fix fundamental file format or parsing errors.

2. Step 2: Identify cause of failure

   If file format is wrong, Snowflake cannot parse data, causing load failure despite ON_ERROR.

3. Final Answer:

   The file format is incorrect causing parsing errors. -> Option B

4. Quick Check:

   Wrong file format causes failure despite ON_ERROR [OK]

Hint: Check file format if ON_ERROR skip_row still fails [OK]

Common Mistakes:

• Thinking ON_ERROR fixes all errors
• Believing ON_ERROR only works for JSON
• Ignoring table existence errors

5. You want to load multiple CSV files but skip any file with more than 10 bad rows, while loading others fully. Which ON_ERROR setting should you use?

hard

A. ON_ERROR = 'continue' with MAX_ERROR = 10

B. ON_ERROR = 'skip_row' with MAX_ERROR = 10

C. ON_ERROR = 'skip_file' with MAX_ERROR = 10

D. ON_ERROR = 'abort_load' with MAX_ERROR = 10

Solution

1. Step 1: Understand requirement

   Skip entire files only if bad rows exceed 10, otherwise load fully.

2. Step 2: Match ON_ERROR and MAX_ERROR

   Using ON_ERROR = 'skip_file' with MAX_ERROR = 10 skips files exceeding 10 errors, loads others fully.

3. Final Answer:

   ON_ERROR = 'skip_file' with MAX_ERROR = 10 -> Option C

4. Quick Check:

   Skip files over 10 errors = skip_file + MAX_ERROR [OK]

Hint: Use skip_file with MAX_ERROR to limit bad rows per file [OK]

Common Mistakes:

• Using skip_row which skips rows, not files
• Assuming 'continue' skips files
• Thinking abort_load allows skipping