Relational databases provides storing data into related data tables.

▪ Relational database tables have a fixed schema, use SQL to manage data and support transactions with ACID principles.

▪ A table uses columns and rows for storing the actual data. Each table will have a column that must have unique values—known as the primary key.

▪ When one table’s primary key is used in another table, this column in the second table is known as the foreign key.

▪ On microservices, we should not consider using single big relational database.

▪ The main advantages of Relational database is ACID compliance. If one change fails, the whole transaction will fail.

▪ Polyglot persistence in microservices, still relational databases is good option some certain type of problems.

▪ Example of relational databases are Oracle, MS SQL Server, MySQL, PostgreSQL.

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