Databases

• PostgreSQL - (PostgreSQL object-relational database system)
• MySQL - (MySQL Community Edition)
• SqlServer - (Microsoft SQL Server)
• Firebird - (Firebird - The RDBMS that's going where you're going)

SQL (Structured Query Language)

• SQL Query Reference and Programming Examples
• SQL in a Nutshell: Chapter 4: SQL Functions

Isolation

• Isolation (database systems)
• Practical Guide to SQL Transaction Isolation

PostgreSQL specific isolation and locks

• https://www.2ndquadrant.com/en/blog/postgresql-anti-patterns-read-modify-write-cycles/
• https://www.postgresql.org/docs/9.5/transaction-iso.html
• https://www.postgresql.org/docs/current/explicit-locking.html#LOCKING-TABLES
• https://www.postgresql.org/docs/current/sql-lock.html

Distributed Transactions

• Two-Phase Commit Mechanism - Oracle.com