Shulou(Shulou.com)05/31 Report--

In this issue, the editor will bring you about the common connections and connection types in the database. The article is rich in content and analyzes and describes for you from a professional point of view. I hope you can get something after reading this article.

What are the common connections and connection types in the database

Join conditions (join condition) can be divided into two categories, depending on the operators used in the connection:

Equal connections (equijion) use the equal and operator (=) in the connection.

Does not mean that non-equijion uses operators other than the equal sign in the connection, such as, BETWEEN, and so on.

In addition to the distinction between connection conditions, there are three different types of connections themselves:

Inner join (inner join) returns a row only if the column in the join contains a value that meets the join condition. This means that if one of the join conditions of a row is a null value, the row will not return.

External joins (outer join) return a row even if a column in the join contains null values.

Self join returns rows connected to the same table.

About not equal to connection

Unequal joins use operators other than the equal operator in the join, including not equal to (), less than (), less than or equal to (=), LIKE, IN, and BETWEEN.

These are the common connections and connection types in the database shared by the editor. If you happen to have similar doubts, please refer to the above analysis to understand. If you want to know more about it, you are welcome to follow the industry information channel.

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