Category: PostgreSQL

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...

The BETWEEN operator. You already know =, LIKE, IN, >, < … Now comes BETWEEN — which is basically a shorthand for two comparison operators combined with AND. Let’s go step-by-step like we’re sitting...