Multiple-to-many queries, three-table queries, and mysql statements

Multi-to-many queries, three-table queries, evaluate mysql statements for common applications: articles and tag data tables, and then query a tag, such as "technology", to query all technical articles.

Article table article:

Aid, title, content ------------------------------------- 1 Qt assists in cross-platform application development, 2 Qt assists in cross-platform application development, 3 Qt assists in cross-platform application development, and 4 Qt assists in cross-platform application development.

Label table tags:

Tid, tname -------------------------------- 1 life 2 technology 3 Technology 4 Entertainment

Article tag relationship table art_tags:

aid，tid----------------------------1 11 21 32 12 32 43 13 23 44 14 2

Then, search for the keyword "technology" based on the tag and display the articles 1, 3, and 4.

Reply to discussion (solution)

Select a. * from article as a left join art_tags at on at. aid = a. aid where at. tid = 2

Select a. * from article as a left join art_tags at on at. aid = a. aid where at. tid = 2

At. tid = 2? This cannot be known in advance. The user inputs the Chinese character "technology"

Select * from article where aid in (select aid from art_tags where tid in (select tid from tags where tname = ''));

Select a. * from article a left join art_tags B on a. aid = B. aid left join tags c on c. tid = B. tid where B. tname =''

Thank you!
The original where statement can also be written like this.