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Lesson 6 +10 XP

WHERE Clause

WHERE Clause

The WHERE clause filters records: it only keeps the rows that match a condition.

Basic example

SELECT * FROM Customers
WHERE Country = 'Mexico';

This returns only the customers whose Country is exactly 'Mexico'.

Text vs numbers

  • Text: WHERE City = 'Berlin'
  • Numbers: WHERE CustomerID = 3
  • Operators: =, <, >, <=, >=, <> (not equal), != 
SELECT * FROM Products
WHERE Price > 30;

The full SELECT order

KeywordPurpose
SELECTchoose columns
FROMchoose table
WHEREfilter rows

WHERE with a column you don't select

You can filter on a column that isn't in the result:

SELECT CustomerName FROM Customers
WHERE Country = 'Germany';

The result only shows names, but only German customers are included.

TL;DR

  • WHERE filters rows based on a condition.
  • Text needs quotes: WHERE Country = 'Mexico'.
  • Comparison operators: =, <>, >, <, >=, <=.