A common problem stems from trying to use an identifier such as a table or column name that is the name of a built-in MySQL data type or function, such as TIMESTAMP or GROUP. You're allowed to do this (for example, ABS is allowed as a column name). However, by default, no whitespace is allowed in function invocations between the function name and the following ‘(’ character. This requirement allows a function call to be distinguished from a reference to a column name.

A side effect of this behavior is that omitting a space in some contexts causes an identifier to be interpreted as a function name. For example, this statement is legal:

mysql> CREATE TABLE abs (val INT);

But omitting the space after abs causes a syntax error because the statement then appears to invoke the ABS() function:

mysql> CREATE TABLE abs(val INT);

If the server SQL mode includes the IGNORE_SPACE mode value, the server allows function invocations to have whitespace between a function name and the following ‘(’ character. This causes function names to be treated as reserved words. As a result, identifiers that are the same as function names must be quoted as described in the section called “Database, Table, Index, Column, and Alias Names”. The server SQL mode is controlled as described in the section called “The Server SQL Mode”.

The words in the following table are explicitly reserved in MySQL. Most of them are forbidden by standard SQL as column and/or table names (for example, GROUP). A few are reserved because MySQL needs them and (currently) uses a yacc parser. A reserved word can be used as an identifier if you quote it.

MySQL allows some keywords to be used as unquoted identifiers because many people have already used them. Examples are those in the following list: