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所在平台: Udemy |
课程主页: https://www.udemy.com/course/practical-hands-on-microsoft-sql-joins-sql-server-ssms/
课程评论：没有评论
课程名称：Microsoft SQL 连接实用操作：SQL Server, SSMS 课程概述： 本课程专注于讲解SQL中的连接（JOIN）语句，这是组合两个或多个表中数据或行的关键技术，其依据是它们之间存在的公共字段。课程将详细介绍不同类型的连接： * **INNER JOIN (内连接)**: 仅返回两个表中满足连接条件的行。即，只有当公共字段的值在两个表中都存在时，才会将行组合起来。 * **OUTER JOIN (外连接)**: * **LEFT JOIN (左连接 / 左外连接)**: 返回左表中的所有行，以及右表中与之匹配的行。如果右表中没有匹配的行，则右表的字段将显示为NULL。 * **RIGHT JOIN (右连接 / 右外连接)**: 返回右表中的所有行，以及左表中与之匹配的行。如果左表中没有匹配的行，则左表的字段将显示为NULL。 * **FULL JOIN (全连接)**: 结合了LEFT JOIN和RIGHT JOIN的结果，返回两个表中的所有行。如果在其中一个表中不存在匹配的行，则该表对应的字段将显示为NULL。 本课程将通过Microsoft SQL Server和SSMS（SQL Server Management Studio）进行实际操作演示，帮助学习者掌握这些不同连接方式的应用。
SQL Join statement is used to combine data or rows from two or more tables based on a common field between them. Different types of Joins are as follows: INNER JOINLEFT JOINRIGHT JOINFULL JOINThe INNER JOIN keyword selects all rows from both the tables as long as the condition is satisfied. This keyword will create the result-set by combining all rows from both the tables where the condition satisfies i.e value of the common field will be the same. The OUTER JOIN returns all the rows of the table on the left side of the join and matches rows for the table on the right side of the join. For the rows for which there is no matching row on the right side, the result-set will contain null. LEFT JOIN is also known as LEFT OUTER JOIN.RIGHT JOIN is similar to LEFT JOIN. This join returns all the rows of the table on the right side of the join and matching rows for the table on the left side of the join. For the rows for which there is no matching row on the left side, the result-set will contain null. RIGHT JOIN is also known as RIGHT OUTER JOIN. FULL JOIN creates the result-set by combining results of both LEFT JOIN and RIGHT JOIN. The result-set will contain all the rows from both tables. For the rows for which there is no matching, the result-set will contain NULL values.
