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Choose a SQL reference by what you need to do: review core queries, prepare data, combine tables, analyze rows with window functions, or get ready for an interview. The five resources described in KDnuggets’ January 19, 2024 roundup cover those different needs; the fifth is an interview-question collection, not a cheat sheet. Treat them as refreshers, then practice writing queries to build proficiency.
Which SQL reference should you choose?
| When you need to… | Reference | What it covers |
|---|---|---|
| Refresh core SQL syntax and operations | LearnSQL basics reference | Filtering, aggregation and grouping, subqueries, and set operations, alongside single- and multi-table queries. |
| Prepare or reshape data | KDnuggets data-preparation reference | Dataset profiling, validation, standardization, attribute creation and derivation, combining datasets, and splitting them. |
| Understand how tables and result sets are combined | DataCamp joins reference | Inner, self, left, full, and cross joins; UNION, UNION ALL, INTERSECT, and EXCEPT. |
| Calculate values across related rows | DataCamp window-functions reference | PARTITION BY, ORDER BY, window frames, ranking, value and aggregate functions, LEAD, and LAG. |
| Review topics for an SQL interview | Edureka interview-question collection | Database relationships, schemas, constraints, normalization, OLAP and OLTP, indexes, optimization, triggers, subqueries, stored procedures, and SQL Server- and PostgreSQL-specific questions. |
These descriptions reflect the recommendations in Bala Priya C’s January 19, 2024 KDnuggets roundup. It does not establish whether every linked page remains available today, nor does it compare their formats, prices, or layouts.
SQL basics: refresh everyday querying
The LearnSQL reference is the most foundational choice in the roundup. Its coverage includes querying one table and multiple tables, filtering results, grouping and aggregation, subqueries, and set operations. Use it when you need a quick reminder of syntax or want to check which core operation fits a query.
Data preparation: review the work before analysis
The KDnuggets reference, attributed to Stan Pugsley, focuses on preparing datasets. The listed topics include profiling data, validating and standardizing it, creating or deriving attributes, combining datasets, and splitting them. This makes it relevant when the task is getting data into a usable form rather than simply retrieving rows.
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SQL joins: combine tables and result sets
The DataCamp joins reference spans two related but distinct ideas. It lists inner, self, left, full, and cross joins for combining rows from tables, as well as UNION, UNION ALL, INTERSECT, and EXCEPT for set operations on query results. If you are unsure whether a task calls for a join or a set operator, this is the category to revisit.
Window functions: calculate across rows without collapsing them
The DataCamp window-functions reference is for a more specialized analytics task. According to the roundup, it covers syntax; ordering and partitioning; window-frame extent; ranking, value, and aggregate functions; and LEAD and LAG. Its inclusion of both frame concepts and function families makes it useful when a calculation depends on a row’s place within an ordered group.
SQL interview questions: use the collection for review
The Edureka resource is not a cheat sheet; it is a collection of interview questions. The roundup describes questions on database relationships, schemas, constraints, normalization, OLAP versus OLTP, indexes, query optimization, triggers, subqueries, and stored procedures, including SQL Server- and PostgreSQL-specific questions. It is therefore better suited to interview-topic review than to looking up a syntax pattern while writing a query.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How to refresh your SQL skills
- Pick one task. Decide whether you are querying, preparing data, joining tables, analyzing rows, or reviewing interview topics.
- Use the matching reference to check a concept. Look up the relevant syntax or topic rather than trying to memorize an entire sheet at once.
- Write and test queries. A reference can remind you how an operation works, but practice is needed to build proficiency.
That distinction is central to the roundup: a sheet helps with recall, while repeated hands-on use develops skill.
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