diff --git a/src/UserGuide/Master/Table/Basic-Concept/Table-Management.md b/src/UserGuide/Master/Table/Basic-Concept/Table-Management.md index 16a1cd825..3bce6199c 100644 --- a/src/UserGuide/Master/Table/Basic-Concept/Table-Management.md +++ b/src/UserGuide/Master/Table/Basic-Concept/Table-Management.md @@ -34,7 +34,7 @@ Manually create a table within the current or specified database.The format is " ```SQL CREATE TABLE (IF NOT EXISTS)? '(' (columnDefinition (',' columnDefinition)*)? ')' - (WITH properties)? + (COMMENT 'TABLE_COMMENT')? (WITH properties)? columnDefinition : identifier columnCategory=(TAG | ATTRIBUTE) @@ -65,6 +65,7 @@ property 3. Names with special or Chinese characters must be enclosed in double quotes (`""`). 4. Outer double quotes are not retained in the final table name. For example: `"a""b"` becomes `a"b`. 5. **`columnDefinition`**: Column names share the same characteristics as table names and can include special characters such as `.`. +6. COMMENT adds comments to the table. **Examples:** @@ -80,7 +81,7 @@ CREATE TABLE table1 ( humidity FLOAT FIELD, status Boolean FIELD, arrival_time TIMESTAMP FIELD -) WITH (TTL=31536000000); +) COMMENT 'table1' WITH (TTL=31536000000); CREATE TABLE if not exists table2 (); @@ -153,17 +154,17 @@ After the code execution is complete, you can use the following statement to ver ```SQL IoTDB> desc table1 -+-----------+---------+-----------+ -| ColumnName| DataType| Category| -+-----------+---------+-----------+ -| time|TIMESTAMP| TIME| -| region_id| STRING| TAG| -| plant_id| STRING| TAG| -| device_id| STRING| TAG| -| model| STRING| ATTRIBUTE| -|temperature| FLOAT| FIELD| -| humidity| DOUBLE| FIELD| -+-----------+---------+-----------+ ++-----------+---------+-----------+-------+ +| ColumnName| DataType| Category|Comment| ++-----------+---------+-----------+-------+ +| time|TIMESTAMP| TIME| null| +| region_id| STRING| TAG| null| +| plant_id| STRING| TAG| null| +| device_id| STRING| TAG| null| +| model| STRING| ATTRIBUTE| null| +|temperature| FLOAT| FIELD| null| +| humidity| DOUBLE| FIELD| null| ++-----------+---------+-----------+-------+ ``` ### 1.2 View Tables @@ -189,20 +190,20 @@ SHOW TABLES (DETAILS)? ((FROM | IN) database_name)? ```SQL IoTDB> show tables from test_db -+---------+-------+ -|TableName|TTL(ms)| -+---------+-------+ -| test| INF| -+---------+-------+ ++---------+-------+-------+ +|TableName|TTL(ms)|Comment| ++---------+-------+-------+ +| test| INF| TEST| ++---------+-------+-------+ IoTDB> show tables details from test_db -+---------+-------+----------+ -|TableName|TTL(ms)| Status| -+---------+-------+----------+ -| test| INF| USING| -| turbine| INF|PRE_CREATE| -| car| 1000|PRE_DELETE| -+---------+-------+----------+ ++---------+-------+----------+-------+ +|TableName|TTL(ms)| Status|Comment| ++---------+-------+----------+-------+ +| test| INF| USING| TEST| +| turbine| INF|PRE_CREATE| null| +| car| 1000|PRE_DELETE| null| ++---------+-------+----------+-------+ ``` ### 1.3 View Table Columns @@ -226,24 +227,25 @@ Used to view column names, data types, categories, and states of a table. ```SQL IoTDB> desc tableB -+----------+---------+-----------+ -|ColumnName| DataType| Category|d -| time|TIMESTAMP| TIME| -| a| STRING| TAG| -| b| STRING| ATTRIBUTE| -| c| INT32| FIELD| -+----------+---------+-----------+ ++----------+---------+-----------+-------+ +|ColumnName| DataType| Category|Comment| ++----------+---------+-----------+-------+ +| time|TIMESTAMP| TIME| null| +| a| STRING| TAG| a| +| b| STRING| ATTRIBUTE| b| +| c| INT32| FIELD| c| ++----------+---------+-----------+-------+ IoTDB> desc tableB details -+----------+---------+-----------+----------+ -|ColumnName| DataType| Category| Status| -+----------+---------+-----------+----------+ -| time|TIMESTAMP| TIME| USING| -| a| STRING| TAG| USING| -| b| STRING| ATTRIBUTE| USING| -| c| INT32| FIELD| USING| -| d| INT32| FIELD|PRE_DELETE| -+----------+---------+-----------+----------+ ++----------+---------+-----------+----------+-------+ +|ColumnName| DataType| Category| Status|Comment| ++----------+---------+-----------+----------+-------+ +| time|TIMESTAMP| TIME| USING| null| +| a| STRING| TAG| USING| a| +| b| STRING| ATTRIBUTE| USING| b| +| c| INT32| FIELD| USING| c| +| d| INT32| FIELD|PRE_DELETE| d| ++----------+---------+-----------+----------+-------+ ``` ### 1.4 Update Tables @@ -257,18 +259,23 @@ ALTER TABLE (IF EXISTS)? tableName=qualifiedName ADD COLUMN (IF NOT EXISTS)? col | ALTER TABLE (IF EXISTS)? tableName=qualifiedName DROP COLUMN (IF EXISTS)? column=identifier #dropColumn // set TTL can use this | ALTER TABLE (IF EXISTS)? tableName=qualifiedName SET PROPERTIES propertyAssignments #setTableProperties +| COMMENT ON TABLE tableName=qualifiedName IS 'table_comment' +| COMMENT ON COLUMN tableName.column IS 'column_comment' ``` **Note:：** 1. The `SET PROPERTIES` operation currently only supports configuring the `TTL` property of a table 2. The delete column function only supports deleting the ATTRIBUTE and FILD columns, and the TAG column does not support deletion. +3. The modified comment will overwrite the original comment. If null is specified, the previous comment will be erased. **Example:** ```SQL ALTER TABLE tableB ADD COLUMN IF NOT EXISTS a TAG ALTER TABLE tableB set properties TTL=3600 +COMMENT ON TABLE table1 IS 'table1' +COMMENT ON COLUMN table1.a IS null ``` ### 1.5 Delete Tables diff --git a/src/UserGuide/latest-Table/Basic-Concept/Table-Management.md b/src/UserGuide/latest-Table/Basic-Concept/Table-Management.md index 16a1cd825..3bce6199c 100644 --- a/src/UserGuide/latest-Table/Basic-Concept/Table-Management.md +++ b/src/UserGuide/latest-Table/Basic-Concept/Table-Management.md @@ -34,7 +34,7 @@ Manually create a table within the current or specified database.The format is " ```SQL CREATE TABLE (IF NOT EXISTS)? '(' (columnDefinition (',' columnDefinition)*)? ')' - (WITH properties)? + (COMMENT 'TABLE_COMMENT')? (WITH properties)? columnDefinition : identifier columnCategory=(TAG | ATTRIBUTE) @@ -65,6 +65,7 @@ property 3. Names with special or Chinese characters must be enclosed in double quotes (`""`). 4. Outer double quotes are not retained in the final table name. For example: `"a""b"` becomes `a"b`. 5. **`columnDefinition`**: Column names share the same characteristics as table names and can include special characters such as `.`. +6. COMMENT adds comments to the table. **Examples:** @@ -80,7 +81,7 @@ CREATE TABLE table1 ( humidity FLOAT FIELD, status Boolean FIELD, arrival_time TIMESTAMP FIELD -) WITH (TTL=31536000000); +) COMMENT 'table1' WITH (TTL=31536000000); CREATE TABLE if not exists table2 (); @@ -153,17 +154,17 @@ After the code execution is complete, you can use the following statement to ver ```SQL IoTDB> desc table1 -+-----------+---------+-----------+ -| ColumnName| DataType| Category| -+-----------+---------+-----------+ -| time|TIMESTAMP| TIME| -| region_id| STRING| TAG| -| plant_id| STRING| TAG| -| device_id| STRING| TAG| -| model| STRING| ATTRIBUTE| -|temperature| FLOAT| FIELD| -| humidity| DOUBLE| FIELD| -+-----------+---------+-----------+ ++-----------+---------+-----------+-------+ +| ColumnName| DataType| Category|Comment| ++-----------+---------+-----------+-------+ +| time|TIMESTAMP| TIME| null| +| region_id| STRING| TAG| null| +| plant_id| STRING| TAG| null| +| device_id| STRING| TAG| null| +| model| STRING| ATTRIBUTE| null| +|temperature| FLOAT| FIELD| null| +| humidity| DOUBLE| FIELD| null| ++-----------+---------+-----------+-------+ ``` ### 1.2 View Tables @@ -189,20 +190,20 @@ SHOW TABLES (DETAILS)? ((FROM | IN) database_name)? ```SQL IoTDB> show tables from test_db -+---------+-------+ -|TableName|TTL(ms)| -+---------+-------+ -| test| INF| -+---------+-------+ ++---------+-------+-------+ +|TableName|TTL(ms)|Comment| ++---------+-------+-------+ +| test| INF| TEST| ++---------+-------+-------+ IoTDB> show tables details from test_db -+---------+-------+----------+ -|TableName|TTL(ms)| Status| -+---------+-------+----------+ -| test| INF| USING| -| turbine| INF|PRE_CREATE| -| car| 1000|PRE_DELETE| -+---------+-------+----------+ ++---------+-------+----------+-------+ +|TableName|TTL(ms)| Status|Comment| ++---------+-------+----------+-------+ +| test| INF| USING| TEST| +| turbine| INF|PRE_CREATE| null| +| car| 1000|PRE_DELETE| null| ++---------+-------+----------+-------+ ``` ### 1.3 View Table Columns @@ -226,24 +227,25 @@ Used to view column names, data types, categories, and states of a table. ```SQL IoTDB> desc tableB -+----------+---------+-----------+ -|ColumnName| DataType| Category|d -| time|TIMESTAMP| TIME| -| a| STRING| TAG| -| b| STRING| ATTRIBUTE| -| c| INT32| FIELD| -+----------+---------+-----------+ ++----------+---------+-----------+-------+ +|ColumnName| DataType| Category|Comment| ++----------+---------+-----------+-------+ +| time|TIMESTAMP| TIME| null| +| a| STRING| TAG| a| +| b| STRING| ATTRIBUTE| b| +| c| INT32| FIELD| c| ++----------+---------+-----------+-------+ IoTDB> desc tableB details -+----------+---------+-----------+----------+ -|ColumnName| DataType| Category| Status| -+----------+---------+-----------+----------+ -| time|TIMESTAMP| TIME| USING| -| a| STRING| TAG| USING| -| b| STRING| ATTRIBUTE| USING| -| c| INT32| FIELD| USING| -| d| INT32| FIELD|PRE_DELETE| -+----------+---------+-----------+----------+ ++----------+---------+-----------+----------+-------+ +|ColumnName| DataType| Category| Status|Comment| ++----------+---------+-----------+----------+-------+ +| time|TIMESTAMP| TIME| USING| null| +| a| STRING| TAG| USING| a| +| b| STRING| ATTRIBUTE| USING| b| +| c| INT32| FIELD| USING| c| +| d| INT32| FIELD|PRE_DELETE| d| ++----------+---------+-----------+----------+-------+ ``` ### 1.4 Update Tables @@ -257,18 +259,23 @@ ALTER TABLE (IF EXISTS)? tableName=qualifiedName ADD COLUMN (IF NOT EXISTS)? col | ALTER TABLE (IF EXISTS)? tableName=qualifiedName DROP COLUMN (IF EXISTS)? column=identifier #dropColumn // set TTL can use this | ALTER TABLE (IF EXISTS)? tableName=qualifiedName SET PROPERTIES propertyAssignments #setTableProperties +| COMMENT ON TABLE tableName=qualifiedName IS 'table_comment' +| COMMENT ON COLUMN tableName.column IS 'column_comment' ``` **Note:：** 1. The `SET PROPERTIES` operation currently only supports configuring the `TTL` property of a table 2. The delete column function only supports deleting the ATTRIBUTE and FILD columns, and the TAG column does not support deletion. +3. The modified comment will overwrite the original comment. If null is specified, the previous comment will be erased. **Example:** ```SQL ALTER TABLE tableB ADD COLUMN IF NOT EXISTS a TAG ALTER TABLE tableB set properties TTL=3600 +COMMENT ON TABLE table1 IS 'table1' +COMMENT ON COLUMN table1.a IS null ``` ### 1.5 Delete Tables diff --git a/src/zh/UserGuide/Master/Table/Basic-Concept/Table-Management.md b/src/zh/UserGuide/Master/Table/Basic-Concept/Table-Management.md index c2b59707a..e48b2b19e 100644 --- a/src/zh/UserGuide/Master/Table/Basic-Concept/Table-Management.md +++ b/src/zh/UserGuide/Master/Table/Basic-Concept/Table-Management.md @@ -34,7 +34,7 @@ ```SQL CREATE TABLE (IF NOT EXISTS)? '(' (columnDefinition (',' columnDefinition)*)? ')' - (WITH properties)? + (COMMENT 'TABLE_COMMENT')? (WITH properties)? columnDefinition : identifier columnCategory=(TAG | ATTRIBUTE) @@ -69,6 +69,7 @@ property """""" --> "" ``` 5. columnDefinition 列名称与表名称具有相同特性，并且可包含特殊字符`.`。 +6. COMMENT 给表添加注释。 **示例:** @@ -84,7 +85,7 @@ CREATE TABLE table1 ( humidity FLOAT FIELD, status Boolean FIELD, arrival_time TIMESTAMP FIELD -) WITH (TTL=31536000000); +) COMMENT 'table1' WITH (TTL=31536000000); CREATE TABLE if not exists table2 (); @@ -157,17 +158,17 @@ try (ITableSession session = ```SQL IoTDB> desc table1 -+-----------+---------+-----------+ -| ColumnName| DataType| Category| -+-----------+---------+-----------+ -| time|TIMESTAMP| TIME| -| region_id| STRING| TAG| -| plant_id| STRING| TAG| -| device_id| STRING| TAG| -| model| STRING| ATTRIBUTE| -|temperature| FLOAT| FIELD| -| humidity| DOUBLE| FIELD| -+-----------+---------+-----------+ ++-----------+---------+-----------+-------+ +| ColumnName| DataType| Category|Comment| ++-----------+---------+-----------+-------+ +| time|TIMESTAMP| TIME| null| +| region_id| STRING| TAG| null| +| plant_id| STRING| TAG| null| +| device_id| STRING| TAG| null| +| model| STRING| ATTRIBUTE| null| +|temperature| FLOAT| FIELD| null| +| humidity| DOUBLE| FIELD| null| ++-----------+---------+-----------+-------+ ``` ### 1.2 查看表 @@ -193,20 +194,20 @@ SHOW TABLES (DETAILS)? ((FROM | IN) database_name)? ```SQL IoTDB> show tables from test_db -+---------+-------+ -|TableName|TTL(ms)| -+---------+-------+ -| test| INF| -+---------+-------+ ++---------+-------+-------+ +|TableName|TTL(ms)|Comment| ++---------+-------+-------+ +| test| INF| TEST| ++---------+-------+-------+ IoTDB> show tables details from test_db -+---------+-------+----------+ -|TableName|TTL(ms)| Status| -+---------+-------+----------+ -| test| INF| USING| -| turbine| INF|PRE_CREATE| -| car| 1000|PRE_DELETE| -+---------+-------+----------+ ++---------+-------+----------+-------+ +|TableName|TTL(ms)| Status|Comment| ++---------+-------+----------+-------+ +| test| INF| USING| TEST| +| turbine| INF|PRE_CREATE| null| +| car| 1000|PRE_DELETE| null| ++---------+-------+----------+-------+ ``` ### 1.3 查看表的列 @@ -229,25 +230,25 @@ IoTDB> show tables details from test_db ```SQL IoTDB> desc tableB -+----------+---------+-----------+ -|ColumnName| DataType| Category| -+----------+---------+-----------+ -| time|TIMESTAMP| TIME| -| a| STRING| TAG| -| b| STRING| ATTRIBUTE| -| c| INT32| FIELD| -+----------+---------+-----------+ ++----------+---------+-----------+-------+ +|ColumnName| DataType| Category|Comment| ++----------+---------+-----------+-------+ +| time|TIMESTAMP| TIME| null| +| a| STRING| TAG| a| +| b| STRING| ATTRIBUTE| b| +| c| INT32| FIELD| c| ++----------+---------+-----------+-------+ IoTDB> desc tableB details -+----------+---------+-----------+----------+ -|ColumnName| DataType| Category| Status| -+----------+---------+-----------+----------+ -| time|TIMESTAMP| TIME| USING| -| a| STRING| TAG| USING| -| b| STRING| ATTRIBUTE| USING| -| c| INT32| FIELD| USING| -| d| INT32| FIELD|PRE_DELETE| -+----------+---------+-----------+----------+ ++----------+---------+-----------+----------+-------+ +|ColumnName| DataType| Category| Status|Comment| ++----------+---------+-----------+----------+-------+ +| time|TIMESTAMP| TIME| USING| null| +| a| STRING| TAG| USING| a| +| b| STRING| ATTRIBUTE| USING| b| +| c| INT32| FIELD| USING| c| +| d| INT32| FIELD|PRE_DELETE| d| ++----------+---------+-----------+----------+-------+ ``` ### 1.4 修改表 @@ -257,22 +258,27 @@ IoTDB> desc tableB details **语法：** ```SQL -ALTER TABLE (IF EXISTS)? tableName=qualifiedName ADD COLUMN (IF NOT EXISTS)? column=columnDefinition #addColumn -| ALTER TABLE (IF EXISTS)? tableName=qualifiedName DROP COLUMN (IF EXISTS)? column=identifier #dropColumn +ALTER TABLE (IF EXISTS)? tableName=qualifiedName ADD COLUMN (IF NOT EXISTS)? column=columnDefinition COMMENT 'column_comment' #addColumn +| ALTER TABLE (IF EXISTS)? tableName=qualifiedName DROP COLUMN (IF EXISTS)? column=identifier #dropColumn // set TTL can use this | ALTER TABLE (IF EXISTS)? tableName=qualifiedName SET PROPERTIES propertyAssignments #setTableProperties +| COMMENT ON TABLE tableName=qualifiedName IS 'table_comment' +| COMMENT ON COLUMN tableName.column IS 'column_comment' ``` **说明：** 1. `SET PROPERTIES`操作目前仅支持对表的 TTL 属性进行配置。 2. 删除列功能，仅支持删除属性列(ATTRIBUTE)和物理量列(FIELD)，标识列(TAG)不支持删除。 +3. 修改后的 comment 会覆盖原有注释，如果指定为 null，则会擦除之前的 comment。 **示例:** ```SQL -ALTER TABLE tableB ADD COLUMN IF NOT EXISTS a TAG +ALTER TABLE tableB ADD COLUMN IF NOT EXISTS a TAG COMMENT 'a' ALTER TABLE tableB set properties TTL=3600 +COMMENT ON TABLE table1 IS 'table1' +COMMENT ON COLUMN table1.a IS null ``` ### 1.5 删除表 diff --git a/src/zh/UserGuide/latest-Table/Basic-Concept/Table-Management.md b/src/zh/UserGuide/latest-Table/Basic-Concept/Table-Management.md index c2b59707a..e48b2b19e 100644 --- a/src/zh/UserGuide/latest-Table/Basic-Concept/Table-Management.md +++ b/src/zh/UserGuide/latest-Table/Basic-Concept/Table-Management.md @@ -34,7 +34,7 @@ ```SQL CREATE TABLE (IF NOT EXISTS)? '(' (columnDefinition (',' columnDefinition)*)? ')' - (WITH properties)? + (COMMENT 'TABLE_COMMENT')? (WITH properties)? columnDefinition : identifier columnCategory=(TAG | ATTRIBUTE) @@ -69,6 +69,7 @@ property """""" --> "" ``` 5. columnDefinition 列名称与表名称具有相同特性，并且可包含特殊字符`.`。 +6. COMMENT 给表添加注释。 **示例:** @@ -84,7 +85,7 @@ CREATE TABLE table1 ( humidity FLOAT FIELD, status Boolean FIELD, arrival_time TIMESTAMP FIELD -) WITH (TTL=31536000000); +) COMMENT 'table1' WITH (TTL=31536000000); CREATE TABLE if not exists table2 (); @@ -157,17 +158,17 @@ try (ITableSession session = ```SQL IoTDB> desc table1 -+-----------+---------+-----------+ -| ColumnName| DataType| Category| -+-----------+---------+-----------+ -| time|TIMESTAMP| TIME| -| region_id| STRING| TAG| -| plant_id| STRING| TAG| -| device_id| STRING| TAG| -| model| STRING| ATTRIBUTE| -|temperature| FLOAT| FIELD| -| humidity| DOUBLE| FIELD| -+-----------+---------+-----------+ ++-----------+---------+-----------+-------+ +| ColumnName| DataType| Category|Comment| ++-----------+---------+-----------+-------+ +| time|TIMESTAMP| TIME| null| +| region_id| STRING| TAG| null| +| plant_id| STRING| TAG| null| +| device_id| STRING| TAG| null| +| model| STRING| ATTRIBUTE| null| +|temperature| FLOAT| FIELD| null| +| humidity| DOUBLE| FIELD| null| ++-----------+---------+-----------+-------+ ``` ### 1.2 查看表 @@ -193,20 +194,20 @@ SHOW TABLES (DETAILS)? ((FROM | IN) database_name)? ```SQL IoTDB> show tables from test_db -+---------+-------+ -|TableName|TTL(ms)| -+---------+-------+ -| test| INF| -+---------+-------+ ++---------+-------+-------+ +|TableName|TTL(ms)|Comment| ++---------+-------+-------+ +| test| INF| TEST| ++---------+-------+-------+ IoTDB> show tables details from test_db -+---------+-------+----------+ -|TableName|TTL(ms)| Status| -+---------+-------+----------+ -| test| INF| USING| -| turbine| INF|PRE_CREATE| -| car| 1000|PRE_DELETE| -+---------+-------+----------+ ++---------+-------+----------+-------+ +|TableName|TTL(ms)| Status|Comment| ++---------+-------+----------+-------+ +| test| INF| USING| TEST| +| turbine| INF|PRE_CREATE| null| +| car| 1000|PRE_DELETE| null| ++---------+-------+----------+-------+ ``` ### 1.3 查看表的列 @@ -229,25 +230,25 @@ IoTDB> show tables details from test_db ```SQL IoTDB> desc tableB -+----------+---------+-----------+ -|ColumnName| DataType| Category| -+----------+---------+-----------+ -| time|TIMESTAMP| TIME| -| a| STRING| TAG| -| b| STRING| ATTRIBUTE| -| c| INT32| FIELD| -+----------+---------+-----------+ ++----------+---------+-----------+-------+ +|ColumnName| DataType| Category|Comment| ++----------+---------+-----------+-------+ +| time|TIMESTAMP| TIME| null| +| a| STRING| TAG| a| +| b| STRING| ATTRIBUTE| b| +| c| INT32| FIELD| c| ++----------+---------+-----------+-------+ IoTDB> desc tableB details -+----------+---------+-----------+----------+ -|ColumnName| DataType| Category| Status| -+----------+---------+-----------+----------+ -| time|TIMESTAMP| TIME| USING| -| a| STRING| TAG| USING| -| b| STRING| ATTRIBUTE| USING| -| c| INT32| FIELD| USING| -| d| INT32| FIELD|PRE_DELETE| -+----------+---------+-----------+----------+ ++----------+---------+-----------+----------+-------+ +|ColumnName| DataType| Category| Status|Comment| ++----------+---------+-----------+----------+-------+ +| time|TIMESTAMP| TIME| USING| null| +| a| STRING| TAG| USING| a| +| b| STRING| ATTRIBUTE| USING| b| +| c| INT32| FIELD| USING| c| +| d| INT32| FIELD|PRE_DELETE| d| ++----------+---------+-----------+----------+-------+ ``` ### 1.4 修改表 @@ -257,22 +258,27 @@ IoTDB> desc tableB details **语法：** ```SQL -ALTER TABLE (IF EXISTS)? tableName=qualifiedName ADD COLUMN (IF NOT EXISTS)? column=columnDefinition #addColumn -| ALTER TABLE (IF EXISTS)? tableName=qualifiedName DROP COLUMN (IF EXISTS)? column=identifier #dropColumn +ALTER TABLE (IF EXISTS)? tableName=qualifiedName ADD COLUMN (IF NOT EXISTS)? column=columnDefinition COMMENT 'column_comment' #addColumn +| ALTER TABLE (IF EXISTS)? tableName=qualifiedName DROP COLUMN (IF EXISTS)? column=identifier #dropColumn // set TTL can use this | ALTER TABLE (IF EXISTS)? tableName=qualifiedName SET PROPERTIES propertyAssignments #setTableProperties +| COMMENT ON TABLE tableName=qualifiedName IS 'table_comment' +| COMMENT ON COLUMN tableName.column IS 'column_comment' ``` **说明：** 1. `SET PROPERTIES`操作目前仅支持对表的 TTL 属性进行配置。 2. 删除列功能，仅支持删除属性列(ATTRIBUTE)和物理量列(FIELD)，标识列(TAG)不支持删除。 +3. 修改后的 comment 会覆盖原有注释，如果指定为 null，则会擦除之前的 comment。 **示例:** ```SQL -ALTER TABLE tableB ADD COLUMN IF NOT EXISTS a TAG +ALTER TABLE tableB ADD COLUMN IF NOT EXISTS a TAG COMMENT 'a' ALTER TABLE tableB set properties TTL=3600 +COMMENT ON TABLE table1 IS 'table1' +COMMENT ON COLUMN table1.a IS null ``` ### 1.5 删除表