- Introduction
- Concepts
- Architecture
- Key Features
- Horizontal Scalability
- MySQL Compatible Syntax
- Replicate from and to MySQL
- Distributed Transactions with Strong Consistency
- Cloud Native Architecture
- Minimize ETL with HTAP
- Fault Tolerance & Recovery with Raft
- Automatic Rebalancing
- Deployment and Orchestration with Ansible, Kubernetes, Docker
- JSON Support
- Spark Integration
- Read Historical Data Without Restoring from Backup
- Fast Import and Restore of Data
- Hybrid of Column and Row Storage
- SQL Plan Management
- Open Source
- Online Schema Changes
- How-to
- Get Started
- Deploy
- Hardware Recommendations
- From Binary Tarball
- Orchestrated Deployment
- Geographic Redundancy
- Data Migration with Ansible
- Configure
- Secure
- Transport Layer Security (TLS)
- Generate Self-signed Certificates
- Monitor
- Migrate
- Maintain
- Common Ansible Operations
- Backup and Restore
- Identify Abnormal Queries
- Scale
- Upgrade
- Troubleshoot
- Reference
- SQL
- MySQL Compatibility
- SQL Language Structure
- Data Types
- Functions and Operators
- Function and Operator Reference
- Type Conversion in Expression Evaluation
- Operators
- Control Flow Functions
- String Functions
- Numeric Functions and Operators
- Date and Time Functions
- Bit Functions and Operators
- Cast Functions and Operators
- Encryption and Compression Functions
- Information Functions
- JSON Functions
- Aggregate (GROUP BY) Functions
- Window Functions
- Miscellaneous Functions
- Precision Math
- List of Expressions for Pushdown
- SQL Statements
ADD COLUMN
ADD INDEX
ADMIN
ADMIN CANCEL DDL
ADMIN CHECKSUM TABLE
ADMIN CHECK [TABLE|INDEX]
ADMIN SHOW DDL [JOBS|QUERIES]
ALTER DATABASE
ALTER TABLE
ALTER USER
ANALYZE TABLE
BEGIN
CHANGE COLUMN
COMMIT
CREATE DATABASE
CREATE INDEX
CREATE ROLE
CREATE TABLE LIKE
CREATE TABLE
CREATE USER
CREATE VIEW
DEALLOCATE
DELETE
DESC
DESCRIBE
DO
DROP COLUMN
DROP DATABASE
DROP INDEX
DROP ROLE
DROP TABLE
DROP USER
DROP VIEW
EXECUTE
EXPLAIN ANALYZE
EXPLAIN
FLUSH PRIVILEGES
FLUSH STATUS
FLUSH TABLES
GRANT <privileges>
GRANT <role>
INSERT
KILL [TIDB]
LOAD DATA
LOAD STATS
MODIFY COLUMN
PREPARE
RECOVER TABLE
RENAME INDEX
RENAME TABLE
REPLACE
REVOKE <privileges>
REVOKE <role>
ROLLBACK
SELECT
SET DEFAULT ROLE
SET [NAMES|CHARACTER SET]
SET PASSWORD
SET ROLE
SET TRANSACTION
SET [GLOBAL|SESSION] <variable>
SHOW ANALYZE STATUS
SHOW CHARACTER SET
SHOW COLLATION
SHOW [FULL] COLUMNS FROM
SHOW CREATE TABLE
SHOW CREATE USER
SHOW DATABASES
SHOW ENGINES
SHOW ERRORS
SHOW [FULL] FIELDS FROM
SHOW GRANTS
SHOW INDEXES [FROM|IN]
SHOW INDEX [FROM|IN]
SHOW KEYS [FROM|IN]
SHOW PRIVILEGES
SHOW [FULL] PROCESSSLIST
SHOW SCHEMAS
SHOW STATUS
SHOW [FULL] TABLES
SHOW TABLE REGIONS
SHOW TABLE STATUS
SHOW [GLOBAL|SESSION] VARIABLES
SHOW WARNINGS
SPLIT REGION
START TRANSACTION
TRACE
TRUNCATE
UPDATE
USE
- Constraints
- Generated Columns
- Partitioning
- Character Set
- SQL Mode
- Views
- Configuration
- Security
- Transactions
- System Databases
- Errors Codes
- Supported Client Drivers
- Garbage Collection (GC)
- Performance
- Overview
- Understanding the Query Execution Plan
- The Blocklist of Optimization Rules and Expression Pushdown
- Introduction to Statistics
- TopN and Limit Push Down
- Optimizer Hints
- Check the TiDB Cluster Status Using SQL Statements
- Execution Plan Binding
- Statement Summary Table
- Tune TiKV
- Operating System Tuning
- Column Pruning
- Key Monitoring Metrics
- Alert Rules
- Best Practices
- TiSpark
- TiKV
- TiDB Binlog
- Tools
- TiDB in Kubernetes
- FAQs
- Support
- Contribute
- Releases
- All Releases
- v3.0
- v2.1
- v2.0
- v1.0
- Glossary
You are viewing the documentation of an older version of the TiDB database (TiDB v3.0).
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. Values stored as CHAR
are right-padded with spaces to the specified length. M represents the column-length in characters (not bytes). The range of M is 0 to 255:
[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.
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.
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.