String Types
TiDB supports all the MySQL string types, including CHAR, VARCHAR, BINARY, VARBINARY, BLOB, TEXT, ENUM, and SET. For more information, see String Types in MySQL.
Supported types
CHAR type
CHAR is a fixed length string. M represents the column-length in characters (not bytes). The range of M is 0 to 255. Different from the VARCHAR type, when data is inserted into a CHAR column, the trailing spaces are truncated.
[NATIONAL] CHAR[(M)] [CHARACTER SET charset_name] [COLLATE collation_name]
VARCHAR type
VARCHAR is a string of variable-length. M represents the maximum column length in characters (not bytes). The maximum size of VARCHAR cannot exceed 65,535 bytes. The maximum row length and the character set being used determine the VARCHAR length.
The space occupied by a single character might differ for different character sets. The following table shows the bytes consumed by a single character, and the range of the VARCHAR column length in each character set:
| Character Set | Byte(s) per Character | Range of the Maximum VARCHAR Column Length |
|---|---|---|
| ascii | 1 | (0, 65535] |
| latin1 | 1 | (0, 65535] |
| binary | 1 | (0, 65535] |
| utf8 | 3 | (0, 21845] |
| utf8mb4 | 4 | (0, 16383] |
[NATIONAL] VARCHAR(M) [CHARACTER SET charset_name] [COLLATE collation_name]
TEXT type
TEXT is a string of variable-length. M represents the maximum column length in characters, ranging from 0 to 65,535. The maximum row length and the character set being used determine the TEXT length.
TEXT[(M)] [CHARACTER SET charset_name] [COLLATE collation_name]
TINYTEXT type
The TINYTEXT type is similar to the TEXT type. The difference is that the maximum column length of TINYTEXT is 255.
TINYTEXT [CHARACTER SET charset_name] [COLLATE collation_name]
MEDIUMTEXT type
The MEDIUMTEXT type is similar to the TEXT type. The difference is that the maximum column length of MEDIUMTEXT is 16,777,215.
MEDIUMTEXT [CHARACTER SET charset_name] [COLLATE collation_name]
LONGTEXT type
The LONGTEXT type is similar to the TEXT type. The difference is that the maximum column length of LONGTEXT is 4,294,967,295. But due to the Limitation on a single column in TiDB, the maximum storage size of a single column in TiDB is 6 MB.
LONGTEXT [CHARACTER SET charset_name] [COLLATE collation_name]
BINARY type
The BINARY type is similar to the CHAR type. The difference is that BINARY stores binary byte strings.
BINARY(M)
VARBINARY type
The VARBINARY type is similar to the VARCHAR type. The difference is that the VARBINARY stores binary byte strings.
VARBINARY(M)
BLOB type
BLOB is a large binary file. M represents the maximum column length in bytes, ranging from 0 to 65,535.
BLOB[(M)]
TINYBLOB type
The TINYBLOB type is similar to the BLOB type. The difference is that the maximum column length of TINYBLOB is 255.
TINYBLOB
MEDIUMBLOB type
The MEDIUMBLOB type is similar to the BLOB type. The difference is that the maximum column length of MEDIUMBLOB is 16,777,215.
MEDIUMBLOB
LONGBLOB type
The LONGBLOB type is similar to the BLOB type. The difference is that the maximum column length of LONGBLOB is 4,294,967,295. But due to the Limitation on a single column in TiDB, the maximum storage size of a single column in TiDB is 6 MB.
LONGBLOB
ENUM type
An ENUM is a string object with a value chosen from a list of permitted values that are enumerated explicitly in the column specification when the table is created. The syntax is:
ENUM('value1','value2',...) [CHARACTER SET charset_name] [COLLATE collation_name]
# For example:
ENUM('apple', 'orange', 'pear')
The value of the ENUM data type is stored as numbers. Each value is converted to a number according the definition order. In the previous example, each string is mapped to a number:
| Value | Number |
|---|---|
| NULL | NULL |
| '' | 0 |
| 'apple' | 1 |
| 'orange' | 2 |
| 'pear' | 3 |
For more information, see the ENUM type in MySQL.
SET type
A SET is a string object that can have zero or more values, each of which must be chosen from a list of permitted values specified when the table is created. The syntax is:
SET('value1','value2',...) [CHARACTER SET charset_name] [COLLATE collation_name]
# For example:
SET('1', '2') NOT NULL
In the example, any of the following values can be valid:
''
'1'
'2'
'1,2'
In TiDB, the values of the SET type is internally converted to Int64. The existence of each element is represented using a binary: 0 or 1. For a column specified as SET('a','b','c','d'), the members have the following decimal and binary values.
| Member | Decimal Value | Binary Value |
|---|---|---|
| 'a' | 1 | 0001 |
| 'b' | 2 | 0010 |
| 'c' | 4 | 0100 |
| 'd' | 8 | 1000 |
In this case, for an element of ('a', 'c'), it is 0101 in binary.
For more information, see the SET type in MySQL.