For different types of connection strings explained in full, please visit https://www.connectionstrings.com 

Here are some examples of connection string formats, however these are not exhaustive. 

SQL Server

"Server=[myServerName];Database=[myDatabase];User Id=[myUsername];Password=[myPassword];Trust Server Certificate=true;" 

PostgreSQL

"host=[myServerName];Port=[myPortNumber];Database=[myDatabase];User Id=[myUsername];Password=[myPassword];" 

MySQL

"Server=[myServerName];Database=[myDatabase];Uid=[myUsername];Pwd=[myPassword];" 

Oracle

"DATA SOURCE=[myServerName]/[myDatabase];USER ID=[myUsername];PASSWORD=[myPassword];"