- About TiDB
- Quick Start
- Deploy
- Software and Hardware Requirements
- Environment Configuration Checklist
- Plan Cluster Topology
- Install and Start
- Verify Cluster Status
- Test Cluster Performance
- Migrate
- Overview
- Migrate from MySQL
- Migrate from CSV Files
- Migrate from SQL Files
- Replicate Incremental Data between TiDB Clusters in Real Time
- Maintain
- Upgrade
- Scale
- Backup and Restore
- Use BR Tool (Recommended)
- Configure Time Zone
- Daily Checklist
- Maintain TiFlash
- Maintain TiDB Using TiUP
- Modify Configuration Online
- Online Unsafe Recovery
- Monitor and Alert
- Troubleshoot
- TiDB Troubleshooting Map
- Identify Slow Queries
- Analyze Slow Queries
- SQL Diagnostics
- Identify Expensive Queries
- Statement Summary Tables
- Troubleshoot Hotspot Issues
- Troubleshoot Increased Read and Write Latency
- Save and Restore the On-Site Information of a Cluster
- Troubleshoot Cluster Setup
- Troubleshoot High Disk I/O Usage
- Troubleshoot Lock Conflicts
- Troubleshoot TiFlash
- Troubleshoot Write Conflicts in Optimistic Transactions
- Performance Tuning
- System Tuning
- Software Tuning
- SQL Tuning
- Overview
- Understanding the Query Execution Plan
- SQL Optimization Process
- Overview
- Logic Optimization
- Physical Optimization
- Prepare Execution Plan Cache
- Control Execution Plans
- Tutorials
- Multiple Data Centers in One City Deployment
- Three Data Centers in Two Cities Deployment
- Two Data Centers in One City Deployment
- Read Historical Data
- Use Stale Read (Recommended)
- Use the
tidb_snapshot
System Variable
- Best Practices
- Use Placement Rules
- Use Load Base Split
- Use Store Limit
- TiDB Tools
- Overview
- Use Cases
- Download
- TiUP
- TiDB Operator
- Backup & Restore (BR)
- TiDB Binlog
- TiDB Lightning
- TiDB Data Migration
- TiCDC
- Dumpling
- sync-diff-inspector
- TiSpark
- Reference
- Cluster Architecture
- Key Monitoring Metrics
- Secure
- Privileges
- SQL
- SQL Language Structure and Syntax
- SQL Statements
ADD COLUMN
ADD INDEX
ADMIN
ADMIN CANCEL DDL
ADMIN CHECKSUM TABLE
ADMIN CHECK [TABLE|INDEX]
ADMIN SHOW DDL [JOBS|QUERIES]
ADMIN SHOW TELEMETRY
ALTER DATABASE
ALTER INDEX
ALTER INSTANCE
ALTER PLACEMENT POLICY
ALTER TABLE
ALTER USER
ANALYZE TABLE
BACKUP
BEGIN
CHANGE COLUMN
COMMIT
CHANGE DRAINER
CHANGE PUMP
CREATE [GLOBAL|SESSION] BINDING
CREATE DATABASE
CREATE INDEX
CREATE PLACEMENT POLICY
CREATE ROLE
CREATE SEQUENCE
CREATE TABLE LIKE
CREATE TABLE
CREATE USER
CREATE VIEW
DEALLOCATE
DELETE
DESC
DESCRIBE
DO
DROP [GLOBAL|SESSION] BINDING
DROP COLUMN
DROP DATABASE
DROP INDEX
DROP PLACEMENT POLICY
DROP ROLE
DROP SEQUENCE
DROP STATS
DROP TABLE
DROP USER
DROP VIEW
EXECUTE
EXPLAIN ANALYZE
EXPLAIN
FLASHBACK TABLE
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
RESTORE
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 [BACKUPS|RESTORES]
SHOW [GLOBAL|SESSION] BINDINGS
SHOW BUILTINS
SHOW CHARACTER SET
SHOW COLLATION
SHOW [FULL] COLUMNS FROM
SHOW CONFIG
SHOW CREATE PLACEMENT POLICY
SHOW CREATE SEQUENCE
SHOW CREATE TABLE
SHOW CREATE USER
SHOW DATABASES
SHOW DRAINER STATUS
SHOW ENGINES
SHOW ERRORS
SHOW [FULL] FIELDS FROM
SHOW GRANTS
SHOW INDEX [FROM|IN]
SHOW INDEXES [FROM|IN]
SHOW KEYS [FROM|IN]
SHOW MASTER STATUS
SHOW PLACEMENT
SHOW PLACEMENT FOR
SHOW PLACEMENT LABELS
SHOW PLUGINS
SHOW PRIVILEGES
SHOW [FULL] PROCESSSLIST
SHOW PROFILES
SHOW PUMP STATUS
SHOW SCHEMAS
SHOW STATS_HEALTHY
SHOW STATS_HISTOGRAMS
SHOW STATS_META
SHOW STATUS
SHOW TABLE NEXT_ROW_ID
SHOW TABLE REGIONS
SHOW TABLE STATUS
SHOW [FULL] TABLES
SHOW [GLOBAL|SESSION] VARIABLES
SHOW WARNINGS
SHUTDOWN
SPLIT REGION
START TRANSACTION
TABLE
TRACE
TRUNCATE
UPDATE
USE
WITH
- Data Types
- Functions and Operators
- Overview
- 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
- Set Operations
- List of Expressions for Pushdown
- TiDB Specific Functions
- Clustered Indexes
- Constraints
- Generated Columns
- SQL Mode
- Table Attributes
- Transactions
- Garbage Collection (GC)
- Views
- Partitioning
- Temporary Tables
- Character Set and Collation
- Placement Rules in SQL
- System Tables
mysql
- INFORMATION_SCHEMA
- Overview
ANALYZE_STATUS
CLIENT_ERRORS_SUMMARY_BY_HOST
CLIENT_ERRORS_SUMMARY_BY_USER
CLIENT_ERRORS_SUMMARY_GLOBAL
CHARACTER_SETS
CLUSTER_CONFIG
CLUSTER_HARDWARE
CLUSTER_INFO
CLUSTER_LOAD
CLUSTER_LOG
CLUSTER_SYSTEMINFO
COLLATIONS
COLLATION_CHARACTER_SET_APPLICABILITY
COLUMNS
DATA_LOCK_WAITS
DDL_JOBS
DEADLOCKS
ENGINES
INSPECTION_RESULT
INSPECTION_RULES
INSPECTION_SUMMARY
KEY_COLUMN_USAGE
METRICS_SUMMARY
METRICS_TABLES
PARTITIONS
PLACEMENT_RULES
PROCESSLIST
REFERENTIAL_CONSTRAINTS
SCHEMATA
SEQUENCES
SESSION_VARIABLES
SLOW_QUERY
STATISTICS
TABLES
TABLE_CONSTRAINTS
TABLE_STORAGE_STATS
TIDB_HOT_REGIONS
TIDB_INDEXES
TIDB_SERVERS_INFO
TIDB_TRX
TIFLASH_REPLICA
TIKV_REGION_PEERS
TIKV_REGION_STATUS
TIKV_STORE_STATUS
USER_PRIVILEGES
VIEWS
METRICS_SCHEMA
- UI
- TiDB Dashboard
- Overview
- Maintain
- Access
- Overview Page
- Cluster Info Page
- Key Visualizer Page
- Metrics Relation Graph
- SQL Statements Analysis
- Slow Queries Page
- Cluster Diagnostics
- Search Logs Page
- Instance Profiling
- Session Management and Configuration
- FAQ
- CLI
- Command Line Flags
- Configuration File Parameters
- System Variables
- Storage Engines
- Telemetry
- Errors Codes
- Table Filter
- Schedule Replicas by Topology Labels
- FAQs
- Release Notes
- All Releases
- Release Timeline
- v5.3
- v5.2
- v5.1
- v5.0
- v4.0
- v3.1
- v3.0
- v2.1
- v2.0
- v1.0
- Glossary
CHANGE COLUMN
The ALTER TABLE.. CHANGE COLUMN
statement changes a column on an existing table. The change can include both renaming the column, and changing the data type to a compatible type.
Since v5.1.0, TiDB has supported changing the Reorg data type, including but not limited to:
- Changing
VARCHAR
toBIGINT
- Modifying the
DECIMAL
precision - Compressing the length of
VARCHAR(10)
toVARCHAR(5)
Synopsis
- AlterTableStmt
- AlterTableSpec
- ColumnName
- ColumnDef
- ColumnPosition
AlterTableStmt ::=
'ALTER' IgnoreOptional 'TABLE' TableName ( AlterTableSpecListOpt AlterTablePartitionOpt | 'ANALYZE' 'PARTITION' PartitionNameList ( 'INDEX' IndexNameList )? AnalyzeOptionListOpt )
AlterTableSpec ::=
TableOptionList
| 'SET' 'TIFLASH' 'REPLICA' LengthNum LocationLabelList
| 'CONVERT' 'TO' CharsetKw ( CharsetName | 'DEFAULT' ) OptCollate
| 'ADD' ( ColumnKeywordOpt IfNotExists ( ColumnDef ColumnPosition | '(' TableElementList ')' ) | Constraint | 'PARTITION' IfNotExists NoWriteToBinLogAliasOpt ( PartitionDefinitionListOpt | 'PARTITIONS' NUM ) )
| ( ( 'CHECK' | 'TRUNCATE' ) 'PARTITION' | ( 'OPTIMIZE' | 'REPAIR' | 'REBUILD' ) 'PARTITION' NoWriteToBinLogAliasOpt ) AllOrPartitionNameList
| 'COALESCE' 'PARTITION' NoWriteToBinLogAliasOpt NUM
| 'DROP' ( ColumnKeywordOpt IfExists ColumnName RestrictOrCascadeOpt | 'PRIMARY' 'KEY' | 'PARTITION' IfExists PartitionNameList | ( KeyOrIndex IfExists | 'CHECK' ) Identifier | 'FOREIGN' 'KEY' IfExists Symbol )
| 'EXCHANGE' 'PARTITION' Identifier 'WITH' 'TABLE' TableName WithValidationOpt
| ( 'IMPORT' | 'DISCARD' ) ( 'PARTITION' AllOrPartitionNameList )? 'TABLESPACE'
| 'REORGANIZE' 'PARTITION' NoWriteToBinLogAliasOpt ReorganizePartitionRuleOpt
| 'ORDER' 'BY' AlterOrderItem ( ',' AlterOrderItem )*
| ( 'DISABLE' | 'ENABLE' ) 'KEYS'
| ( 'MODIFY' ColumnKeywordOpt IfExists | 'CHANGE' ColumnKeywordOpt IfExists ColumnName ) ColumnDef ColumnPosition
| 'ALTER' ( ColumnKeywordOpt ColumnName ( 'SET' 'DEFAULT' ( SignedLiteral | '(' Expression ')' ) | 'DROP' 'DEFAULT' ) | 'CHECK' Identifier EnforcedOrNot | 'INDEX' Identifier IndexInvisible )
| 'RENAME' ( ( 'COLUMN' | KeyOrIndex ) Identifier 'TO' Identifier | ( 'TO' | '='? | 'AS' ) TableName )
| LockClause
| AlgorithmClause
| 'FORCE'
| ( 'WITH' | 'WITHOUT' ) 'VALIDATION'
| 'SECONDARY_LOAD'
| 'SECONDARY_UNLOAD'
ColumnName ::=
Identifier ( '.' Identifier ( '.' Identifier )? )?
ColumnDef ::=
ColumnName ( Type | 'SERIAL' ) ColumnOptionListOpt
ColumnPosition ::=
( 'FIRST' | 'AFTER' ColumnName )?
Examples
CREATE TABLE t1 (id int not null primary key AUTO_INCREMENT, col1 INT);
Query OK, 0 rows affected (0.11 sec)
INSERT INTO t1 (col1) VALUES (1),(2),(3),(4),(5);
Query OK, 5 rows affected (0.02 sec)
Records: 5 Duplicates: 0 Warnings: 0
ALTER TABLE t1 CHANGE col1 col2 INT;
Query OK, 0 rows affected (0.09 sec)
ALTER TABLE t1 CHANGE col2 col3 BIGINT, ALGORITHM=INSTANT;
Query OK, 0 rows affected (0.08 sec)
ALTER TABLE t1 CHANGE col3 col4 BIGINT, CHANGE id id2 INT NOT NULL;
ERROR 1105 (HY000): can't run multi schema change
CREATE TABLE t (a int primary key);
ALTER TABLE t CHANGE COLUMN a a VARCHAR(10);
ERROR 8200 (HY000): Unsupported modify column: column has primary key flag
CREATE TABLE t (c1 INT, c2 INT, c3 INT) partition by range columns(c1) ( partition p0 values less than (10), partition p1 values less than (maxvalue));
ALTER TABLE t CHANGE COLUMN c1 c1 DATETIME;
ERROR 8200 (HY000): Unsupported modify column: table is partition table
CREATE TABLE t (a INT, b INT as (a+1));
ALTER TABLE t CHANGE COLUMN b b VARCHAR(10);
ERROR 8200 (HY000): Unsupported modify column: column is generated
CREATE TABLE t (a DECIMAL(13, 7));
ALTER TABLE t CHANGE COLUMN a a DATETIME;
ERROR 8200 (HY000): Unsupported modify column: change from original type decimal(13,7) to datetime is currently unsupported yet
MySQL compatibility
- Making multiple changes in a single
ALTER TABLE
statement is currently not supported. - Changes of Reorg-Data types on primary key columns are not supported.
- Changes of column types on partitioned tables are not supported.
- Changes of column types on generated columns are not supported.
- Changes of some data types (for example, some TIME, Bit, Set, Enum, and JSON types) are not supported due to the compatibility issues of the
CAST
function's behavior between TiDB and MySQL.
See also
What’s on this page
Was this page helpful?