SQL SELECT

The SELECT keyword allows you to ask a database for data - it is arguably the most basic and important keyword in the SQL language.

Most people start learning SQL by writing SFW (SELECT ... FROM ... WHERE) queries.

Example 1 (specifying columns)

Notice how only the columns we specified are present in the query result.

-- Works in PostgreSQL, MySQL, SQL Server, and Oracle SELECT id, payment_date, dollar_amount FROM rent_payments WHERE dollar_amount >= 1800;

rent_payments table

id tenant_id payment_date dollar_amount
1 1 3/1/2018 2000
2 2 3/2/2018 1500
3 3 3/1/2018 1800
4 4 3/3/2018 1900
5 1 4/2/2018 2000
6 2 4/2/2018 1500
7 3 4/1/2018 1800
8 4 4/2/2018 1900

Query results

id payment_date dollar_amount
1 3/1/2018 2000
3 3/1/2018 1800
4 3/3/2018 1900
5 4/2/2018 2000
7 4/1/2018 1800
8 4/2/2018 1900

Example 2 (SELECT *)

Since we used SELECT *, all columns are present in the query result.

-- Works in PostgreSQL, MySQL, SQL Server, and Oracle SELECT * FROM rent_payments WHERE dollar_amount >= 1800;

rent_payments table

id tenant_id payment_date dollar_amount
1 1 3/1/2018 2000
2 2 3/2/2018 1500
3 3 3/1/2018 1800
4 4 3/3/2018 1900
5 1 4/2/2018 2000
6 2 4/2/2018 1500
7 3 4/1/2018 1800
8 4 4/2/2018 1900

Query results

id tenant_id payment_date dollar_amount
1 1 3/1/2018 2000
3 3 3/1/2018 1800
4 4 3/3/2018 1900
5 1 4/2/2018 2000
7 3 4/1/2018 1800
8 4 4/2/2018 1900