Why data loading is the warehouse foundation in Snowflake - Why It Works

Introduction

Data loading is the first step to get your data into a warehouse. Without loading data correctly, the warehouse cannot store or analyze information. It solves the problem of moving data from different places into one safe spot.

When you want to collect sales data from multiple stores into one place for reports

When you need to update your warehouse daily with new customer information

When you want to combine data from different apps to see the full picture

When you want to clean and organize data before using it for decisions

When you want to make sure your data is ready and available for fast queries

Config File - load_data.sql

load_data.sql

COPY INTO my_table
FROM @my_stage/data.csv
FILE_FORMAT = (TYPE = 'CSV' FIELD_DELIMITER = ',' SKIP_HEADER = 1);

This SQL script loads data from a staged CSV file into a Snowflake table called my_table.

COPY INTO tells Snowflake to load data.

@my_stage/data.csv is the location of the file to load.

FILE_FORMAT defines how the file is structured, here a CSV with commas and skipping the header row.

Commands

This command runs the SQL script to load data into the warehouse using SnowSQL CLI.

Terminal

snowsql -a myaccount -u myuser -f load_data.sql

Expected Output

Copying into table MY_TABLE from @MY_STAGE/data.csv

1 rows loaded successfully.

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-a - Specifies the Snowflake account to connect to

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-u - Specifies the username for authentication

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-f - Specifies the SQL file to execute

This command checks how many rows were loaded into the table to verify the load worked.

Terminal

snowsql -a myaccount -u myuser -q "SELECT COUNT(*) FROM my_table;"

Expected Output

COUNT(*)

----------

1

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-q - Runs a SQL query directly from the command line

Key Concept

If you remember nothing else from this pattern, remember: loading data correctly is the first and most important step to make your warehouse useful.

Common Mistakes

Trying to load data without defining the correct file format

Snowflake cannot understand how to read the file, so the load fails or data is wrong

Always specify the file format details like type, delimiter, and header rows when loading data

Running the load command without staging the data file first

Snowflake cannot find the file to load, so the command errors out

Upload your data file to a Snowflake stage before running the COPY INTO command

Summary

Use COPY INTO command to load data from staged files into Snowflake tables.

Verify data load success by querying the table row count.

Specify file format details to ensure data is read correctly.