DQL / Data Query Language
SQL DQL: Queries and analysis
Build query results with SELECT. Follow inputs, filters, aggregation, window calculations, expressions and output to understand where each clause and function fits.
Topics in this category
Choose and combine inputs
FROM selects an input; JOIN combines tables. WITH and subqueries organize intermediate results. Array expansion also belongs here.
Filter rows and groups
WHERE, HAVING and QUALIFY filter at different stages. Read them with comparisons, logical operators and NULL handling.
Group and aggregate rows
GROUP BY defines groups; COUNT and SUM calculate counts and totals. Distinguish query-level clauses from modifiers inside aggregate calls.
Rank and compare while keeping rows
OVER defines a window; PARTITION BY divides it into groups. Read ranking, neighboring-row comparisons and running totals with their frame specifications.
Transform values
Build expressions with text, numbers, dates, conditions and conversions. Use the function index below to inspect arguments and return values.
Combine and order results
Combine result sets with UNION and other set operators, sort with ORDER BY and limit row counts with LIMIT. Compare set operations with JOIN.
From function categories to individual functions
Choose a category to filter the function map, or a function name to open its details. String and date functions also work in expressions such as UPDATE SET, beyond SELECT.