SQL Server series: multi-table Connection query

Connection queries are the most important queries in relational data, including inner joins, outer joins, and so on. You can implement multiple table queries by using the Join operator. The INNER JOIN query operation lists the data rows that match the join criteria, and it uses comparison operators to compare the column values of the concatenated columns. Internal connections in SQL Server are: equivalent connections and unequal connections.

1. Internal connection-Equal connection

An equal join is also called an equivalent join, in the join condition this uses the equals (=) operator to compare the column values of the concatenated column, and its query results list all the columns in the joined table, including the repeating columns.

Example:

SELECT [dbo].[Category].*,[dbo].[Product].* from [dbo].[Category] INNER JOIN [dbo].[Product] on [dbo].[Category].[CategoryID] = [dbo].[Product].[CategoryID]

SQL Server series: multi-table Connection query