TiDB literal values include character literals, numeric literals, time and date literals, hexadecimal, binary literals, and NULL literals. This document introduces each of these literal values.
This document describes String literals, Numeric literals, NULL values, Hexadecimal literals, Date and time literals, Boolean literals, and Bit-value literals.
A string is a sequence of bytes or characters, enclosed within either single quote
' or double quote
" characters. For example:
'example string' "example string"
Quoted strings placed next to each other are concatenated to a single string. The following lines are equivalent:
'a string' 'a' ' ' 'string' "a" ' ' "string"
ANSI_QUOTES SQL MODE is enabled, string literals can be quoted only within single quotation marks because a string quoted within double quotation marks is interpreted as an identifier.
The string is divided into the following two types:
- Binary string: It consists of a sequence of bytes, whose charset and collation are both
binary, and uses byte as the unit when compared with each other.
- Non-binary string: It consists of a sequence of characters and has various charsets and collations other than
binary. When compared with each other, non-binary strings use characters as the unit. A character might contain multiple bytes, depending on the charset.
A string literal may have an optional
character set introducer and
COLLATE clause, to designate it as a string that uses a specific character set and collation.
[_charset_name]'string' [COLLATE collation_name]
SELECT _latin1'string'; SELECT _binary'string'; SELECT _utf8'string' COLLATE utf8_bin;
You can use N'literal' (or n'literal') to create a string in the national character set. The following statements are equivalent:
SELECT N'some text'; SELECT n'some text'; SELECT _utf8'some text';
To represent some special characters in a string, you can use escape characters to escape:
|\0||An ASCII NUL (X'00') character|
|\'||A single quote |
|\"||A double quote |
|\b||A backspace character|
|\n||A line break (newline) character|
|\r||A carriage return character|
|\t||A tab character|
|\z||ASCII 26 (Ctrl + Z)|
|\\||A backslash |
If you want to represent
" in the string surrounded by
' in the string surrounded by
", you do not need to use escape characters.
For more information, see String Literals in MySQL.
Numeric literals include integer and DECIMAL literals and floating-point literals.
Integer may include
. as a decimal separator. Numbers may be preceded by
+ to indicate a negative or positive value respectively.
Exact-value numeric literals can be represented as
1, .2, 3.4, -5, -6.78, +9.10.
Numeric literals can also be represented in scientific notation, such as
1.2E3, 1.2E-3, -1.2E3, -1.2E-3.
For more information, see Numeric Literals in MySQL.
Date and time literal values can be represented in several formats, such as quoted strings or as numbers. When TiDB expects a date, it interprets any of
20170824 as a date.
TiDB supports the following date formats:
-delimiter here is not strict. It can be any punctuation. For example,
'2012@12^31'are all valid date formats. The only special punctuation is '.', which is is treated as a decimal point to separate the integer and fractional parts. Date and time can be separated by
Tor a white space. For example,
2017-8-24T10:42:00represents the same date and time.
'YYMMDDHHMMSS': For example,
'170824104520'are regarded as
'2017-08-24 10:45:20'. However, if you provide a value out of range, such as
'170824304520', it is not treated as a valid date. Note that incorrect formats such as
YYYYMMDD HH:MM:DD, or
YYYY-MM-DD HHMMSSwill fail to insert.
YYMMDDHHMMSS: Note that these formats have no single or double quotes, but a number. For example,
20170824104520is interpreted as
DATETIME or TIMESTAMP values can be followed by a fractional part, used to represent microseconds precision (6 digits). The fractional part should always be separated from the rest of the time by a decimal point
The year value containing only two digits is ambiguous. It is recommended to use the four-digit year format. TiDB interprets the two-digit year value according to the following rules:
- If the year value is in the range of
70-99, it is converted to
- If the year value is in the range of
00-69, it is converted to
For month or day values less than 10,
'2017-8-4' is the same as
'2017-08-04'. The same is true for Time. For example,
'2017-08-24 1:2:3' is the same as
When the date or time value is required, TiDB selects the specified format according to the length of the value:
- 6 digits:
- 12 digits:
- 8 digits:
- 14 digits:
TiDB supports the following formats for time values:
'D HH:MM:SS', or
Dmeans days and the valid value range is
- A number in
HHMMSSformat: For example,
231010is interpreted as
- A number in any of
HHMMSSformats can be regarded as time.
The decimal point of the Time type is also
., with a precision of up to 6 digits after the decimal point.
See MySQL date and time literals for more details.
FALSE are equal to 1 and 0 respectively, which are not case sensitive.
SELECT TRUE, true, tRuE, FALSE, FaLsE, false;
+------+------+------+-------+-------+-------+ | TRUE | true | tRuE | FALSE | FaLsE | false | +------+------+------+-------+-------+-------+ | 1 | 1 | 1 | 0 | 0 | 0 | +------+------+------+-------+-------+-------+ 1 row in set (0.00 sec)
Hexadecimal literal values are written using
0xval notation, where
val contains hexadecimal digits. A leading
0x is case sensitive and cannot be written as
Legal hexadecimal literals:
X'ac12' X'12AC' x'ac12' x'12AC' 0xac12 0x12AC
Illegal hexadecimal literals:
X'1z' (z is not a hexadecimal legal digit) 0X12AC (0X must be written as 0x)
Hexadecimal literals written using
X'val' notation must contain an even number of digits. If the length of
val is an odd number (for example,
X'11A'), to avoid the syntax error, pad the value with a leading zero:
mysql> select X'aff'; ERROR 1105 (HY000): line 0 column 13 near ""hex literal: invalid hexadecimal format, must even numbers, but 3 (total length 13) mysql> select X'0aff'; +---------+ | X'0aff' | +---------+ | 0x0aff | +---------+ 1 row in set (0.00 sec)
By default, a hexadecimal literal is a binary string.
To convert a string or a number to a string in hexadecimal format, use the
mysql> SELECT HEX('TiDB'); +-------------+ | HEX('TiDB') | +-------------+ | 54694442 | +-------------+ 1 row in set (0.01 sec) mysql> SELECT X'54694442'; +-------------+ | X'54694442' | +-------------+ | TiDB | +-------------+ 1 row in set (0.00 sec)
Bit-value literals are written using
0bval notation. The
val is a binary value written using zeros and ones. A leading
0b is case sensitive and cannot be written as
Legal bit-value literals:
b'01' B'01' 0b01
Illegal bit-value literals:
b'2' (2 is not a binary digit; it must be 0 or 1) 0B01 (0B must be written as 0b)
By default, a bit-value literal is a binary string.
Bit values are returned as binary values, which may not display well in the MySQL client. To convert a bit value to printable form, you can use a conversion function such as
CREATE TABLE t (b BIT(8)); INSERT INTO t SET b = b'00010011'; INSERT INTO t SET b = b'1110'; INSERT INTO t SET b = b'100101'; mysql> SELECT b+0, BIN(b), HEX(b) FROM t; +------+--------+--------+ | b+0 | BIN(b) | HEX(b) | +------+--------+--------+ | 19 | 10011 | 13 | | 14 | 1110 | E | | 37 | 100101 | 25 | +------+--------+--------+ 3 rows in set (0.00 sec)
NULL means the data is empty, which is case-insensitive, and is synonymous with