SQL
Beginner Practice Queries
Twenty graded exercises on SELECT, filtering, sorting and simple functions, each with a worked solution and the reason it is written that way.
#Queries
Reading data with SELECT.
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SQL
Creating and Querying Views
A view is a stored query you can select from like a table. Learn CREATE VIEW, how views are executed, and the four jobs they do well.
SQL
WITH: Single and Multiple CTEs
A CTE names a query so the rest of the statement can read it like a table. Learn single and chained CTEs, and when a CTE beats a subquery or a view.
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GROUP BY Fundamentals
GROUP BY collapses rows into one row per distinct key. Learn the single rule that governs the select list and how NULLs are grouped.
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ORDER BY, LIMIT and Pagination
Sorting on one or many columns, NULL placement, and the four dialect specific ways to fetch page two of a result set - including why OFFSET gets slow.
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Expressions, Calculated Columns and DISTINCT
Compute values in the select list, build derived columns from existing ones, and use DISTINCT correctly - including what it does across several column...
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SELECT Basics: Columns, SELECT * and Aliases
The statement you will write more than all the others combined. Choose columns, alias them, and learn why SELECT * belongs in the console and not in c...
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SQL Operators and Expressions
Arithmetic, comparison, logical, string and set operators, how precedence works, and where an expression may legally appear.
SQL
SQL Syntax, Keywords, Identifiers and Comments
How a SQL statement is built: clause order, keywords versus identifiers, quoting rules, statement terminators and the two comment styles.