初级代码街区

SQL

向你的数据提出任何问题。

SQL is the language of databases. Every post, like and game score in an app like Nova lives in database tables, and SQL is how you ask those tables questions. This track starts from zero: reading tables with SELECT, filtering and sorting, counting and grouping, joining tables, changing data safely, designing your own tables, and finally subqueries, CTEs and window functions.

Every lesson works with the same small dataset from Nova, a made-up social app (users, posts, likes and scores) and shows the exact result of every query, so you always know what answer to expect.

课时: 25
时长: 3 小时
级别: 初级

开始课程 · What is a database?

本课程的内容目前为英文。

铜牌可挑战
银牌可挑战
金牌未解锁

准备好证明自己了吗？

三场考试正等着你：铜牌、银牌和金牌。

前往考试

学完后你将能够

Read and filter any table with SELECT and WHERE
Summarize data with COUNT, SUM, AVG, GROUP BY and HAVING
Combine tables with INNER JOIN and LEFT JOIN
Insert, update and delete rows safely inside transactions
Design tables with keys, constraints and indexes
Build a leaderboard with subqueries, CTEs and window functions

学习旅程

1
第 1 单元
Databases and tables

What a relational database is, how tables are built, and your first SELECT.

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2
第 2 单元
Filtering and sorting

Keep only the rows you want, handle NULL correctly and put results in order.

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3
第 3 单元
Aggregation

Turn many rows into answers: counts, totals, averages and groups.

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4
第 4 单元
Joins

Combine tables: match rows, keep the unmatched ones and find what is missing.

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5
第 5 单元
Changing data

Add, change and remove rows, and use transactions so mistakes can be undone.

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6
第 6 单元
Designing tables

Create tables with the right types, protect them with constraints and speed them up with indexes.

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7
第 7 单元
Powerful queries

Subqueries, EXISTS, CTEs, CASE and window functions for real leaderboards.

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