This topic helps you get started with the SQL language to manage relational database management systems. Basic operations such as creating, populating, querying, and updating tables are described with examples.
More advanced concepts such as views, foreign keys, and transactions are described.
A PolarDB-O is a relational database management system (RDBMS). The system is used to manage data stored in relations. A relation is essentially a mathematical term for a table. Storing data in tables is a common method of database management. Databases can be organized in several ways. Files and directories on Unix-like operating systems form an example of a hierarchical database. Popular development is based on object-oriented databases.
Each table is a named collection of rows. Each row of a specified table has the same set of named columns and each column is of a specific data type. Columns have a fixed order in each row. However, SQL does not guarantee the order of the rows within the table in any way, even though the rows can be explicitly sorted for display.
Tables are grouped into databases. A collection of databases managed by a PolarDB instance compatible with Oracle constitutes a database cluster.