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How do you filter rows by condition?

SQLJunior~1 min read
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Filtering rows by condition in SQL is done with the keyword WHERE. It lets you select only the records that match a given criterion.

Syntax:

sql
SELECT Column1, Column2, ... FROM Table_Name WHERE Condition;

Example conditions

  1. Comparing against a specific value:
sql
SELECT * FROM Employees WHERE Age = 30;
  • Selects every employee whose Age equals 30.
  1. Greater than or less than:
sql
SELECT * FROM Employees WHERE Age > 25;
  • Selects employees older than 25.
  1. Several conditions (AND, OR):
sql
SELECT * FROM Employees WHERE Age > 25 AND DepartmentID = 101;
  • Selects employees older than 25 who work in department 101.
  1. Checking set membership (IN):
sql
SELECT * FROM Employees WHERE DepartmentID IN (101, 102, 103);
  • Selects employees working in departments 101, 102, or 103.
  1. Pattern matching (LIKE):
sql
SELECT * FROM Employees WHERE Name LIKE 'A%';
  • Selects employees whose names start with the letter "A".

Notes:

  • WHERE is applied before grouping (GROUP BY) and sorting (ORDER BY).
  • Different conditions can be combined for precise filtering.

Put simply, WHERE lets you select only the rows that match certain rules or criteria.

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