Author: web-admin

Part 1: What is SELECT DISTINCT? The SELECT DISTINCT clause removes duplicate rows from your query results, returning only unique combinations of the selected columns. The Basic Syntax sql

When you use DISTINCT, PostgreSQL compares each...

Part 1: What is the WHERE Clause? The WHERE clause filters rows from a table based on specified conditions. Only rows that satisfy the condition are included in the result set. The Basic Syntax sql

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Part 1: What is ORDER BY? The ORDER BY clause sorts the result set of a query by one or more columns, in ascending or descending order. It’s the last step in query execution (conceptually), organizing...

Part 1: What is the LIMIT Clause? The LIMIT clause restricts the number of rows returned by a query. It’s typically used with ORDER BY to get meaningful subsets like “top 10 bestsellers” or “most recent 5 orders.”...

Part 1: What are MIN and MAX? MIN returns the minimum (smallest) value in a set of values. MAX returns the maximum (largest) value in a set of values. These are aggregate functions – they operate on a...

Part 1: What is the COUNT Function? The COUNT function returns the number of rows that match a specified condition. It’s an aggregate function that comes in several flavors: COUNT(*) – Counts all rows in a table or group...

Part 1: What is the SUM Function? The SUM function calculates the total sum of a numeric column or expression. It’s an aggregate function that ignores NULL values (treats them as 0 for the sum). The Basic Syntax...

PostgreSQL: the AVG() function ☕📊 You’ve already learned SELECT, GROUP BY, operators, and built small demo tables. Today we focus on how to calculate averages properly — because AVG() looks simple, but people make...

The LIKE operator in PostgreSQL. You’ve already learned SELECT, WHERE, AVG(), operators in general — now let’s master LIKE, because almost every real application needs to do “search-like” queries at some point (product search,...

The IN operator. You already know =, LIKE, BETWEEN, AND/OR… Now comes IN — which basically says: “Is this value equal to any of the values in this list?” It’s the polite, short way...