Join multiple CSVs / TSVs using SQLite

create_db.sql

/**
 * STEP 1: Write queries to import files into an SQLite database
 **/

/* Set file input mode */
.mode tabs

/* Import tables from TSV files */
.import file1.tsv table1
.import file2.tsv table2
.import file3.tsv table3

join.sql

/**
 * STEP 2: Write queries to JOIN 
 **/

/* Set file output mode */
.mode csv
.headers on
/* OPTIONALLY */
/* .output output.csv */

/* JOIN tables together and output to CSV file */
SELECT a.*, b.column2, c.column2, c.column3, c.column4
FROM table1 a
LEFT OUTER JOIN table2 b ON a.column1 = b.column1
LEFT OUTER JOIN table3 c ON a.column1 = c.column1;

join_files.sh

#!/bin/bash

# Run STEP 1
sqlite3 mydatabase.db < create_db.sql

# Run STEP 2
sqlite3 mydatabase.db < join.sql > output.csv