WHERE: Keep Only the Rows You Mean

SELECT … FROM gives you columns — but every row comes along. Real questions are about some rows: the engineers, the orders above €50, the customers in Ghent. WHERE is how you say which.

In one line

WHERE tests a condition against every row and keeps only the rows where it's true. One clause, and your query starts answering real questions.

See it before you write it

Filter the five employees to just the engineers, and three rows fall away:

name	department	salary
Ada	Engineering	62000
Bo	Sales	48000
Cy	Engineering	71000
Di	Sales	52000
Eli	Marketing	45000

WHERE department = 'Engineering'

name	department	salary
Ada	Engineering	62000
Cy	Engineering	71000

Greyed, struck-through rows fail the condition and are dropped; only matching rows pass through.

Try it now — write the query the visual just showed: the name and salary of every employee in Engineering.

Your turn · Exercise

Write the query the visual showed: name and salary of every employee in the Engineering department.

The data

employees

5 rows returned

name	department	salary
Ada	Engineering	62,000
Bo	Sales	48,000
Cy	Engineering	71,000
Di	Sales	52,000
Eli	Marketing	45,000

SELECT name, salary
FROM employees
WHERE ...

Runs in your browser

Numbers compare without quotes

Conditions aren't just = on text. You have <, >, <=, >=, and <> (not equal). Run it, then change 50000 to 60000:

Numeric comparison — no quotes around the number

SELECT name, salary
FROM employees
WHERE salary > 50000

Editable · runs in your browser

Watch out

The single biggest beginner trip-up: text goes in single quotes, numbers don't. WHERE department = Engineering (no quotes) makes the database look for a column named Engineering and errors. WHERE salary > '50000' quotes a number and invites subtle bugs. Text → quotes; numbers → bare.

Read it the way the database does

Even though you write SELECT first, the database thinks: FROM this table → WHERE these rows match → SELECT these columns. "Which table, which rows, which columns" is the order that makes queries easy to reason about — and it's exactly what the workspace's X-ray button shows you, stage by stage.

Your turn

Return the name and salary of every employee in the Sales department.

Your turn · Exercise

Return the name and salary of every employee in the Sales department.

The data

employees

5 rows returned

name	department	salary	city
Ada	Engineering	62,000	Antwerp
Bo	Sales	48,000	Ghent
Cy	Engineering	71,000	Antwerp
Di	Sales	52,000	Bruges
Eli	Marketing	45,000	Ghent

SELECT ...
FROM employees
WHERE ...

Runs in your browser

Check yourself

Which condition is written correctly?

Next: the rows are right — now put them in order.