How to query your csv files using sqlite

2018-07-19T00:00:00+00:00

Prerequistes

Make sure Sqlite3 is already installed
- for linux: sudo apt-get install sqlite3 libsqlite3-dev
- for mac: brew install sqlite3

start sqllite3 shell by running sqlite3

use the .mode command as follows to set it to csv:

.mode csv

use the .import FILE TABLE command to import the data from the city.csv file into the cities table.

Clone my repo for csv files

.import city.csv cities

If the table does not previously exist, the first row of the CSV file is interpreted to be column names and the actual data starts on the second row of the CSV file.

To verify the import, you use the .schema command to display the structure of the cities table.

.schema cities

Query against the imported table by:

SELECT name, population FROM cities;

See if you can spot the problem between these two group of queries (hint: is population order by working?):

SELECT name, population FROM cities order by population desc;
SELECT name, population FROM cities order by population asc;

SELECT name, population FROM cities order by name asc;
SELECT name, population FROM cities order by name desc;

Drop table by:

DROP TABLE cities;

Create cities table again table:

CREATE TABLE cities (
  name Varchar,
  population Int
);

Import csv file again but now in an existing table with population as Int and no headers (if table already exists then first row of csv becomes first data row of the table)

.import city_no_headers.csv cities

Try these queries again. because the table existed with population as Int the order by behaviour is correct:

SELECT name, population FROM cities order by population desc;
SELECT name, population FROM cities order by population asc;

SELECT name, population FROM cities order by name asc;
SELECT name, population FROM cities order by name desc;

For more sql syntax see documentation here

Rupinder Dhariwal

How to query your csv files using sqlite

Prerequistes