SQL Basics: Keywords, Data Types, and Operators Explained for Beginners

A technical guide published on DEV Community covers the foundational building blocks of SQL, including reserved keywords, data types, and operators. SQL keywords such as SELECT, FROM, WHERE, and JOIN form the backbone of database instructions and are conventionally written in uppercase for readability, even though SQL is case-insensitive. Each database column requires a defined data type — such as INT, DECIMAL, VARCHAR, or BOOLEAN — which acts as the first layer of data validation by restricting what values can be stored. Operators, including comparison symbols, logical connectors like AND and OR, and pattern-matching tools like LIKE and BETWEEN, are primarily used in WHERE clauses to filter and compare data. The guide also highlights practical pitfalls, such as floating-point rounding errors with FLOAT and the distinction between NULL, zero, and empty strings.