NULL Values The constants  TRUE  and  FALSE  evaluate to  1  and  0 , respectively. The constant names can be written in any lettercase. mysql>  SELECT TRUE, true, FALSE, false; -> 1, 1, 0, 0 The  NULL  value means “no data.” NULL  can be written in any lettercase. Be aware that the  NULL  value is different from values such as  0  for numeric types or the empty string for string types. For more information, see Section B.3.4.3, “Problems with NULL Values” . For text file import or export operations performed with  LOAD DATA  or  SELECT ... INTO OUTFILE , NULL  is represented by the  \N  sequence. See Section 13.2.7, “LOAD DATA Statement” . For sorting with  ORDER BY ,  NULL  values sort before other values for ascending sorts, after other values for descending sorts. Certain objects within MySQL, including database, table, index, column, alias, view, stored procedure, partition, tablespace, resource group and other object names are known as identifiers. This section describes the permissible syntax for identifiers in MySQL. Section 9.2.1, “Identifier Length Limits” , indicates the maximum length of each type of identifier. Section 9.2.3, “Identifier Case Sensitivity” , describes which types of identifiers are case-sensitive and under what conditions. An identifier may be quoted or unquoted. If an identifier contains special characters or is a reserved word, you  must  quote it whenever you refer to it. (Exception: A reserved word that follows a period in a qualified name must be an identifier, so it need not be quoted.) Reserved words are listed at Section 9.3, “Keywords and Reserved Words” . Internally, identifiers are converted to and are stored as Unicode (UTF-8). The permissible Unicode characters in identifiers are those in the Basic Multilingual Plane (BMP). Supplementary characters are not permitted. Identifiers thus may contain these characters: The identifier quote character is the backtick ( ‘ ): mysql>  SELECT * FROM ‘select‘ WHERE ‘select‘.id > 100; 1869 9.1.7 NULL Values 9.2 Schema Object Names •Permitted characters in unquoted identifiers: •ASCII: [0-9,a-z,A-Z$_] (basic Latin letters, digits 0-9, dollar, underscore) •Extended: U+0080 .. U+FFFF •Permitted characters in quoted identifiers include the full Unicode Basic Multilingual Plane (BMP), except U+0000: •ASCII: U+0001 .. U+007F •Extended: U+0080 .. U+FFFF •ASCII NUL (U+0000) and supplementary characters (U+10000 and higher) are not permitted in quoted or unquoted identifiers. •Identifiers may begin with a digit but unless quoted may not consist solely of digits. •Database, table, and column names cannot end with space characters.