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Discover an efficient method to import multiple CSV files into a PostgreSQL table with a single command, saving time and effort.
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Loading Multiple CSV Files into a Single PostgreSQL Table: A Simple Guide

Working with large datasets often involves importing multiple CSV files into your database. However, if you're using PostgreSQL, this can become tedious if you rely on issuing individual commands for each file. Let's explore a more efficient way to load multiple CSV files into a single table without sacrificing your productivity.

The Problem: Multiple COPY Commands

When you need to import several CSV files into a PostgreSQL table, you might find yourself running commands such as:

[[See Video to Reveal this Text or Code Snippet]]

This repetitive task can consume a lot of time and is prone to errors. You might even try using a wildcard like this:

[[See Video to Reveal this Text or Code Snippet]]

Unfortunately, wildcards in the COPY command do not work as expected in PostgreSQL, leading to more frustration.

The Solution: A Streamlined Approach

There is a more efficient approach to load all CSV files into your PostgreSQL table using a single command. Instead of running separate commands for each file, we can use the cat command combined with the psql command for a streamlined import process. Here’s how to do it:

Step-by-Step Instruction

Open Your Command Line Interface: Start by accessing your terminal or command prompt where you have PostgreSQL installed.

Run the cat Command: This command will concatenate the contents of all the specified CSV files into standard output.

Pipe the Output to psql: We’ll redirect the concatenated output directly into the PostgreSQL COPY command using the stdin option.

Final Command

Here’s the complete command you should use to import all relevant CSV files into the testemail table in one go:

[[See Video to Reveal this Text or Code Snippet]]

Breakdown of the Command

cat /md-data/vamshi/s3data/test_Hash*.csv: This lists all the CSV files that start with test_Hash and concatenates them.

|: The pipe sends the output of the cat command to the next command.

psql -c 'COPY testemail FROM stdin CSV HEADER': This tells PostgreSQL to copy the data from the standard input, treating the first line of CSV files as headers.

Advantages of This Method

Efficiency: Instead of executing multiple commands, you run only one, saving time and reducing the possibility of errors.

Simplicity: The command is straightforward, making it easier to understand and use.

Flexibility: You can easily manage naming conventions since the cat command will handle any changes in the file names.

Conclusion

By using the cat command combined with the PostgreSQL COPY command, you can effectively load multiple CSV files into a single table in a much more efficient way compared to executing multiple individual commands. Whether you're working from the command line or just looking for a better way to manage your database imports, this method streamlines your workflow significantly.

Give this a try the next time you're handling multiple CSV files, and enjoy the time you save!