Selecting all columns

Learn to fetch every column with SELECT *.

Selecting all columns

To fetch all columns from a table you use the * wildcard. It is a shortcut instead of listing every column.

SELECT *
FROM customers;

This returns every column and every row from the customers table. Handy for a quick look but slow on big tables.

All columns are selected from customers.

Selecting all columns — details

SELECT * looks easy but use it with care in production. Three reasons:

Adding a column changes what the query returns
Unneeded columns increase network traffic
The plan loses selectivity

Best practice: name only the columns you need. SELECT * is fine when you explore a table; for APIs or reports, listing only the needed columns is safer and faster.

Exercise Selecting all columns

Write a query that fetches all columns from the customers table.

Show example solution

SELECT *
FROM customers

Test yourself

All columns

SELECT ____
FROM customers;

Show answer

SELECT *
FROM customers;

Which character fetches all columns?
- %
- *
- &
- #
Show answer

* — * selects all columns.
Selecting all columns: match the terms

*

all columns
FROM

table
comma

separate columns
;

end query

Next lesson: Selecting specific columns

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