SQL
Three Valued Logic: TRUE, FALSE and UNKNOWN
SQL conditions return three results, not two. Learn the AND, OR and NOT truth tables, why NOT IN breaks on NULL, and the NULL safe comparison operator...
#Intermediate
Material for readers past the basics.
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HTML
Lazy Loading and Image Performance
Images are usually the heaviest thing on a page. loading, decoding, fetchpriority and preload are four attributes that decide how fast it feels.
HTML
Embedding External Content with iframe
An iframe puts another page inside yours. Learn the YouTube and maps patterns, the title attribute screen readers need, and the sandbox and loading at...
SQL
CASE, COALESCE, NULLIF and Conversion Functions
Conditional logic inside a query, NULL substitution, safe division and explicit type conversion - four tools that remove most procedural code from SQL...
HTML
Responsive Images: srcset, sizes and picture
Stop sending a 2000 pixel photograph to a phone. Learn width descriptors, the sizes attribute the browser cannot work out for itself, and when picture...
SQL
SQL Date and Time Functions
Current date and time, adding and subtracting intervals, differences between dates, extracting parts, and formatting - the least portable corner of SQ...
HTML
Building a Navigation Menu
A menu is a list of links inside a nav element. Learn the markup that makes it accessible, how to mark the current page, and how a dropdown should be...
HTML
Email, Telephone and Download Links
The href attribute understands more than web pages. mailto, tel and the download attribute turn a link into an email draft, a phone call or a saved fi...
HTML
Fragment Links and In Page Navigation
Link to a spot on the same page with an id and a hash. The basis of tables of contents, skip links, footnotes and back to top links.
HTML
Quotations, Code and Preformatted Text
blockquote, q, cite, abbr, code, pre, kbd and samp. Eight elements that make quoted material and technical text mean what it says.
HTML
The Small Text Elements: mark, small, del, ins, sub and sup
Six narrow elements that each solve one problem precisely: highlighting a match, fine print, tracked edits, and characters that sit above or below the...
SQL
ALTER TABLE: Adding, Modifying and Removing Columns
ALTER changes a table that already holds data. Add and drop columns, change types, set defaults and manage constraints without losing rows.