SQL Language Elements

SQL Language Elements

The SQL language is sub-divided into several
language elements, including:
• Clauses, which are in some cases optional, constituent components of statements and queries.
• Expressionswhich can produce either scalar values or tables consisting of columns and rows of data.
• Predicateswhich specify conditions that can be evaluated to SQL three-valued logic (3VL) Boolean truth values and which are used to limit the effects of statements and queries, or to change program flow.
• Queries which retrieve data based on specific criteria.
•Statements which may have a persistent effect on schemas and data, or which may control transactions, program flow, connections, sessions, or diagnostics.
• SQL statements also include the semicolon (";") statement terminator. Though not required on every platform, it is defined as a standard part of the SQL grammar.
• Insignificant whitespace is generally ignored in SQL statements and queries, making it easier to format SQL code for readability.