Backus Paradigm and SQL language

Query the MySQL help document, how to write SQL statements, you need to pay attention to SQL syntax, here you need to know the BNF Backus paradigm.

Backus paradigm: BNF is used to describe computer languages. The basic rules are as follows:

The angle brackets <> are included in the required option. Brackets [] are included in the optional option. The braces {} contain items that can be repeated 0 to countless times.       Vertical Bar | Means to choose an option on either side of it, equivalent to the meaning of "OR". :: = is defined as meaning. MySQL's syntax basically conforms to the Backus paradigm, but there are some differences, as follows: {} denotes the required option,,... Represents the preceding content, repeated multiple times.

Backus Paradigm and SQL language