# Transform between Relational Data and Kv

![left](./student-guide/diagram/02-07-01.png)
------------------------------------------------------------
Another very important task of TiDB Server is the mutual conversion of relational data and KV. The purpose is to store the relational data written by the client as a key value, and to read the key value data in the storage engine and return it to the client as relational data.

Let's use an animation to explain the mutual transformation of relational data and KV.

- Below is a relational table where the number column can be considered a primary key.