Guides / sql

sql Guides

12 guides

beginner

SQL CRUD

Create, read, update, and delete rows with INSERT, UPDATE, and DELETE

SQL SELECT

Query rows and columns from tables with filtering and sorting

SQL WHERE Clause

Filter rows with conditions, operators, and NULL handling

intermediate

SQL Common Table Expressions (CTEs)

Name intermediate result sets with WITH for readable, reusable queries

SQL GROUP BY

Aggregate rows with COUNT, SUM, AVG, and HAVING filters

SQL Indexes

Speed up queries with B-tree indexes and when to add them

SQL JOINs

Combine rows from related tables with INNER, LEFT, and other joins

SQL Subqueries

Nest queries inside other queries to filter, compute, and compare

SQL Transactions

Group statements into atomic, consistent, isolated, durable units of work

SQL Views

Save queries as reusable virtual tables for cleaner, consistent access

SQL Window Functions

Compute running totals, rankings, and comparisons across row windows

advanced

SQL Query Optimization

Read execution plans and tune queries for speed at scale