Some basic concepts

The SELECT statement, unlike INSERT, UPDATE, and DELETE statements, does not modify the data in a database. It simply queries the data. Whereas only one user at a time can modify data, multiple users can query or select the data concurrently. For more information about statements that modify data, see Modify data. The syntax descriptions of the INSERT, UPDATE, and DELETE statements appear in the HCL OneDB™ Guide to SQL: Syntax.

In a relational database, a column is a data element that contains a particular type of information that occurs in every row in the table. A row is a group of related items of information about a single entity across all columns in a database table.

You can select columns and rows from a database table; from a system catalog table, a special table that contains information on the database; or from a view, a virtual table created to contain a customized set of data. System catalog tables are described in the HCL OneDB Guide to SQL: Reference. Views are discussed in the HCL OneDB Database Design and Implementation Guide.