Literals come in the following varieties:
literals may be enclosed either by single or double quotes. If you
wish to be ANSI compatible, you should always use single quotes.
Within a string literal, you may represent special characters through
escape sequences. An escape sequence is a backslash followed by
another character to indicate to MySQL that the second character has
a meaning other than its normal meaning. Table 15-1
shows the MySQL escape sequences. Quotes can also be escaped by
doubling them up:
''quote'''. However, you do
not need to double up on single quotes when the string is enclosed by
string literals, binary literals are enclosed in single or double
quotes. You must use escape sequences in binary data to escape
NUL (ASCII 0),
" (ASCII 34),
' (ASCII 39), and
\ (ASCII 92).
Numbers appear as a sequence of digits.
Negative numbers are preceded by a
- sign and a
. indicates a decimal point. You may also use
scientific notation, as in: -45198.2164e+10.
MySQL also supports the use of hexadecimal
literals in SQL. The way in which that hexadecimal is interpreted is
dependent on the context. In a numeric context, the hexadecimal
literal is treated is a numeric value. In a non-numeric context, it
is treated as a binary value. For example, 0x1 + 1 is 2, but
0x4d7953514c by itself is
The special keyword
NULL signifies a null literal ...