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试用DataCamp for Business课程描述
Understand Data Joining Fundamentals
You will learn how to work with multiple tables in SQL by navigating and extracting data from various tables within a SQL database using various join types, including inner joins, outer joins, and cross joins. With practice, you'll gain the knowledge of how to select the appropriate join method.Explore Advanced Data Manipulation Techniques
Next up, you'll explore set theory principles such as unions, intersects, and except clauses, as well as discover the power of nested queries in SQL. Every step is accompanied by exercises and opportunities to apply the theory and grow your confidence in SQL.先决条件
Intermediate SQL2
横向合并数据
使用 LEFT JOIN 保留所有行
在不丢失任何行的情况下，为基础表补充额外数据，并理解何时选择 left join 是正确的——特别是当主表中的每一行在另一张表中并不一定都有匹配项时。
使用 INNER JOIN 保留匹配行
只合并跨表匹配的行，理解 inner join 与 left join 的区别，并根据未匹配的行是否对你的分析重要，在这两者之间做出选择。
基于多个列进行连接
在没有单一列可以唯一标识匹配行的情况下，能够准确地连接表，并理解选择错误连接列所带来的后果。
Joining Data in SQL
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