CHANGE COLUMN

ALTER TABLE.. CHANGE COLUMN 语句用于在已有表上更改列,包括对列进行重命名,和将数据改为兼容类型。

语法图

AlterTableStmt
ALTERIgnoreOptionalTABLETableNameAlterTableSpecListOptAlterTablePartitionOptANALYZEPARTITIONPartitionNameListINDEXIndexNameListAnalyzeOptionListOpt
AlterTableSpec
TableOptionListSETTIFLASHREPLICALengthNumLocationLabelListCONVERTTOCharsetKwCharsetNameDEFAULTOptCollateADDColumnKeywordOptIfNotExistsColumnDefColumnPosition(TableElementList)ConstraintPARTITIONIfNotExistsNoWriteToBinLogAliasOptPartitionDefinitionListOptPARTITIONSNUMCHECKTRUNCATEPARTITIONOPTIMIZEREPAIRREBUILDPARTITIONNoWriteToBinLogAliasOptAllOrPartitionNameListCOALESCEPARTITIONNoWriteToBinLogAliasOptNUMDROPColumnKeywordOptIfExistsColumnNameRestrictOrCascadeOptPRIMARYKEYPARTITIONIfExistsPartitionNameListKeyOrIndexIfExistsCHECKIdentifierFOREIGNKEYIfExistsSymbolEXCHANGEPARTITIONIdentifierWITHTABLETableNameWithValidationOptIMPORTDISCARDPARTITIONAllOrPartitionNameListTABLESPACEREORGANIZEPARTITIONNoWriteToBinLogAliasOptReorganizePartitionRuleOptORDERBYAlterOrderItem,DISABLEENABLEKEYSMODIFYColumnKeywordOptIfExistsCHANGEColumnKeywordOptIfExistsColumnNameColumnDefColumnPositionALTERColumnKeywordOptColumnNameSETDEFAULTSignedLiteral(Expression)DROPDEFAULTCHECKIdentifierEnforcedOrNotINDEXIdentifierIndexInvisibleRENAMECOLUMNKeyOrIndexIdentifierTOIdentifierTO=ASTableNameLockClauseAlgorithmClauseFORCEWITHWITHOUTVALIDATIONSECONDARY_LOADSECONDARY_UNLOAD
ColumnName
Identifier.Identifier.Identifier
ColumnDef
ColumnNameTypeSERIALColumnOptionListOpt
ColumnPosition
FIRSTAFTERColumnName

示例

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 col3 INT;
ERROR 1105 (HY000): unsupported modify column length 11 is less than origin 20
ALTER TABLE t1 CHANGE col3 col3 BLOB;
ERROR 1105 (HY000): unsupported modify column type 252 not match origin 8
ALTER TABLE t1 CHANGE col3 col4 BIGINT, CHANGE id id2 INT NOT NULL;
ERROR 1105 (HY000): can't run multi schema change

MySQL 兼容性

  • 不支持在单个 ALTER TABLE 语句中进行多个更改。
  • 不支持有损变更,比如从 BIGINT 变为 INTEGER,或者从 VARCHAR(255) 变为 VARCHAR(10)
  • 不支持修改 DECIMAL 类型的精度。
  • 不支持更改 UNSIGNED 属性。

另请参阅