ALTER TABLE ================================ 描述 ----------- 该语句用来修改已存在的表的结构，比如：修改表及表属性、新增列、修改列及属性、删除列等。 格式 ----------- ```javascript alter_table_stmt: ALTER TABLE table_name alter_table_action_list; | RENAME TABLE rename_table_action_list; alter_table_action_list: alter_table_action [, alter_table_action ...] alter_table_action: ADD [COLUMN] {column_definition | (column_definition_list)} | CHANGE [COLUMN] column_name column_definition | MODIFY [COLUMN] column_definition | ALTER [COLUMN] column_name {SET DEFAULT const_value | DROP DEFAULT} | DROP [COLUMN] column_name | ADD [CONSTRAINT [constraint_name]] UNIQUE {INDEX | KEY} [index_name] index_desc | ADD {INDEX | KEY} [index_name] index_desc | ADD FULLTEXT [INDEX | KEY] [index_name] fulltext_index_desc | ALTER INDEX index_name [VISIBLE | INVISIBLE | parallel_clause] | DROP {INDEX | KEY} index_name | ADD PARTITION (range_partition_list) | DROP PARTITION (partition_name_list) | REORGANIZE PARTITION name_list INTO partition_range_or_list | TRUNCATE PARTITION name_list | [SET] table_option_list | RENAME [TO] table_name | DROP TABLEGROUP | DROP FOREIGN KEY fk_name rename_table_action_list: rename_table_action [, rename_table_action ...] rename_table_action: table_name TO table_name column_definition_list: column_definition [, column_definition ...] column_definition: column_name data_type [DEFAULT const_value] [AUTO_INCREMENT] [NULL | NOT NULL] [[PRIMARY] KEY] [UNIQUE [KEY]] comment index_desc: (column_desc_list) [index_type] [index_option_list] fulltext_index_desc: (column_desc_list) CTXCAT(column_desc_list) [index_option_list] column_desc_list: column_desc [, column_desc ...] column_desc: column_name [(length)] [ASC | DESC] index_type: USING BTREE index_option_list: index_option [ index_option ...] index_option: [GLOBAL | LOCAL] | block_size | compression | STORING(column_name_list) | comment table_option_list: table_option [ table_option ...] table_option: | primary_zone | replica_num | table_tablegroup | block_size | compression | AUTO_INCREMENT [=] INT_VALUE | comment | DUPLICATE_SCOPE [=] "none|zone|region|cluster" | parallel_clause parallel_clause: {NOPARALLEL | PARALLEL integer} partition_option: PARTITION BY HASH(expression) [subpartition_option] PARTITIONS partition_count | PARTITION BY KEY([column_name_list]) [subpartition_option] PARTITIONS partition_count | PARTITION BY RANGE {(expression) | COLUMNS (column_name_list)} [subpartition_option] (range_partition_list) subpartition_option: SUBPARTITION BY HASH(expression) SUBPARTITIONS subpartition_count | SUBPARTITION BY KEY(column_name_list) SUBPARTITIONS subpartition_count | SUBPARTITION BY RANGE {(expression) | COLUMNS (column_name_list)} (range_subpartition_list) range_partition_list: range_partition [, range_partition ...] range_partition: PARTITION partition_name VALUES LESS THAN {(expression_list) | MAXVALUE} range_subpartition_list: range_subpartition [, range_subpartition ...] range_subpartition: SUBPARTITION subpartition_name VALUES LESS THAN {(expression_list) | MAXVALUE} expression_list: expression [, expression ...] column_name_list: column_name [, column_name ...] partition_name_list: partition_name [, partition_name ...] partition_count | subpartition_count: INT_VALUE ``` 参数解释 ------------- | **参数** | **描述** | |---------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | ADD \[COLUMN\] | 增加列，目前不支持增加主键列。 | | CHANGE \[COLUMN\] | 修改列名和列属性。 | | MODIFY \[COLUMN\] | 修改列属性。 | | ALTER \[COLUMN\] | 修改列的默认值。 | | DROP \[COLUMN\] | 删除列，不允许删除主键列或者包含索引的列。 | | ADD \[UNIQUE INDEX\] | 增加唯一索引。 | | ADD \[INDEX\] | 增加普通索引 | | ALTER \[INDEX\] | 修改索引属性。 | | ADD \[PARTITION\] | 增加分区。 | | DROP \[PARTITION\] | 删除分区。 | | REORGANIZE \[PARTITION\] | 分区重组。 | | TRUNCATE \[PARTITION\] | 删除分区数据。 | | RENAME \[TO\] table_name | 表重命名。 | | DROP \[TABLEGROUP\] | 删除表组。 | | DROP \[FOREIGN KEY\] | 删除外键。 | | SET BLOCK_SIZE | 设置Partition表BLOCK大小。 | | SET REPLICA_NUM | 设置表的副本数（指表的副本总数）。 | | SET COMPRESSION | 设置表的压缩方式。 | | SET USE_BLOOM_FILTER | 设置是否使用BloomFilter。 | | SET COMMENT | 设置注释信息。 | | SET PROGRESSIVE_MERGE_NUM | 设置渐进合并步数，取值范围是1\~64。 | | parallel_clause | 指定表级别的并行度： * NOPARALLEL：并行度为1，默认配置 * PARALLEL integer：指定并行度，integer 取值大于等于 1。 | 示例 ----------- * 把表 t2 的字段 d 改名为 c，并同时修改字段类型 ```javascript ALTER TABLE t2 CHANGE COLUMN d c CHAR(10); ``` * 增加、删除列 ![image.png](https://help-static-aliyun-doc.aliyuncs.com/assets/img/zh-CN/8401155061/p149172.png "image.png") ```javascript ALTER TABLE test ADD c3 int; ``` ![image.png](https://help-static-aliyun-doc.aliyuncs.com/assets/img/zh-CN/8401155061/p149173.png "image.png") ```javascript ALTER TABLE test DROP c3; ``` ![image.png](https://help-static-aliyun-doc.aliyuncs.com/assets/img/zh-CN/8401155061/p149174.png "image.png") * 设置表格 test 的副本数，并且增加列 c5 ```javascript ALTER TABLE test SET REPLICA_NUM=2, ADD COLUMN c5 INT; ``` * 修改表 t1 的并行度为 2 ```unknow ALTER TABLE t1 PARALLEL 2; ```