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SQL databases store raw values, but real reports rarely display them exactly as stored. Names may need to be capitalized, prices rounded, and dates formatted in a friendlier way. SQL provides built-in functions that transform values directly inside a query, so the database returns exactly what your application or report needs. In this tutorial, you […]
A SELECT statement is not limited to returning columns exactly as they are stored. You can compute new values on the fly — the total price of an order line, a discount, a tax amount, the age of a record, or the concatenation of a first and last name. These calculations happen inside the database […]
When you write SQL queries, the column names in your result often come straight from the table definition. Names such as unit_price or order_date are useful in the database, but they may look technical in a report, or they may collide when you join two tables that both contain a column called id. SQL solves […]
When you filter rows in SQL, you often need to match a value against a list of options, check whether it falls within a range, or exclude rows that satisfy a condition. Chaining many AND/OR comparisons for these cases quickly becomes hard to read. SQL provides three operators — IN, BETWEEN, and NOT — that […]
When you filter data with WHERE, exact comparisons such as = are not always enough. You often need to find rows where a text column starts with, ends with, or contains a certain fragment. For example, you may want every customer whose email ends with @gmail.com, or every book whose title begins with “The”. SQL […]
When you write SQL, every meaningful query eventually needs a condition — a boolean expression that decides which rows are returned, updated, or deleted. Conditions are built from two small but essential building blocks: comparison operators (=, <>, <, >, <=, >=) and logical operators (AND, OR, NOT). In this tutorial you will learn what […]
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