元数据操作

1. 数据库管理

1.1 创建数据库

语法：

CREATE DATABASE (IF NOT EXISTS)? <DATABASE_NAME> (WITH properties)?

更多详细语法说明请参考：创建数据库

示例：

CREATE DATABASE database1;
CREATE DATABASE IF NOT EXISTS database1;

-- 创建一个名为 database1 的数据库，并将数据库的TTL时间设置为1年。
CREATE DATABASE IF NOT EXISTS database1 with(TTL=31536000000);

1.2 使用数据库

语法：

USE <DATABASE_NAME>

示例:

USE database1

1.3 查看当前数据库

语法：

SHOW CURRENT_DATABASE

示例：

IoTDB> SHOW CURRENT_DATABASE;
+---------------+
|CurrentDatabase|
+---------------+
|           null|
+---------------+

IoTDB> USE test;

IoTDB> SHOW CURRENT_DATABASE;
+---------------+
|CurrentDatabase|
+---------------+
|   iot_database|
+---------------+

1.4 查看所有数据库

语法：

SHOW DATABASES (DETAILS)?

更多返回结果详细说明请参考：查看所有数据库

示例:

IoTDB> show databases
+---------+-------+-----------------------+---------------------+---------------------+
| Database|TTL(ms)|SchemaReplicationFactor|DataReplicationFactor|TimePartitionInterval|
+---------+-------+-----------------------+---------------------+---------------------+
|test_prop|    300|                      3|                    2|               100000|
|    test2|    300|                      3|                    2|            604800000|
+---------+-------+-----------------------+---------------------+---------------------+
IoTDB> show databases details
+---------+-------+-----------------------+---------------------+---------------------+-----------------------+-----------------------+
| Database|TTL(ms)|SchemaReplicationFactor|DataReplicationFactor|TimePartitionInterval|SchemaRegionGroupNum|  DataRegionGroupNum|
+---------+-------+-----------------------+---------------------+---------------------+-----------------------+-----------------------+
|test_prop|    300|                      3|                    2|               100000|                      1|                      2|
|    test2|    300|                      3|                    2|            604800000|                      1|                      2|
+---------+-------+-----------------------+---------------------+---------------------+-----------------------+-----------------------+

1.5 修改数据库

语法：

ALTER DATABASE (IF EXISTS)? database=identifier SET PROPERTIES propertyAssignments

示例:

ALTER DATABASE database1 SET PROPERTIES TTL=31536000000;

1.6 删除数据库

语法：

DROP DATABASE (IF EXISTS)? <DATABASE_NAME>

示例:

DROP DATABASE IF EXISTS database1

2. 表管理

2.1 创建表

语法：

createTableStatement
    : CREATE TABLE (IF NOT EXISTS)? qualifiedName
        '(' (columnDefinition (',' columnDefinition)*)? ')'
        charsetDesc?
        comment?
        (WITH properties)?
     ;

charsetDesc
    : DEFAULT? (CHAR SET | CHARSET | CHARACTER SET) EQ? identifierOrString
    ;

columnDefinition
    : identifier columnCategory=(TAG | ATTRIBUTE | TIME) charsetName? comment?
    | identifier type (columnCategory=(TAG | ATTRIBUTE | TIME | FIELD))? charsetName? comment?
    ;

charsetName
    : CHAR SET identifier
    | CHARSET identifier
    | CHARACTER SET identifier
    ;

comment
    : COMMENT string
    ;

更多详细语法说明请参考：创建表

示例:

CREATE TABLE table1 (
  time TIMESTAMP TIME,
  region STRING TAG,
  plant_id STRING TAG,
  device_id STRING TAG,
  model_id STRING ATTRIBUTE,
  maintenance STRING ATTRIBUTE COMMENT 'maintenance',
  temperature FLOAT FIELD COMMENT 'temperature',
  humidity FLOAT FIELD COMMENT 'humidity',
  status Boolean FIELD COMMENT 'status',
  arrival_time TIMESTAMP FIELD COMMENT 'arrival_time'
) COMMENT 'table1' WITH (TTL=31536000000);

CREATE TABLE if not exists table2 ();

CREATE TABLE tableC (
  "场站" STRING TAG,
  "温度" int32 FIELD COMMENT 'temperature'
 ) with (TTL=DEFAULT);

2.2 查看表

语法：

SHOW TABLES (DETAILS)? ((FROM | IN) database_name)?

示例:

IoTDB> show tables from test_db
+---------+-------+-------+
|TableName|TTL(ms)|Comment|
+---------+-------+-------+
|     test|    INF|   TEST|
+---------+-------+-------+

IoTDB> show tables details from test_db
+---------+-------+----------+-------+
|TableName|TTL(ms)|    Status|Comment|
+---------+-------+----------+-------+
|     test|    INF|     USING|   TEST|
|  turbine|    INF|PRE_CREATE|   null|
|      car|   1000|PRE_DELETE|   null|
+---------+-------+----------+-------+

2.3 查看表的列

语法：

(DESC | DESCRIBE) <TABLE_NAME> (DETAILS)?

示例:

IoTDB> desc tableB
+----------+---------+-----------+-------+
|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|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|
+----------+---------+-----------+----------+-------+

2.4 修改表

语法：

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'

示例:

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

2.5 删除表

语法：

DROP TABLE (IF EXISTS)? <TABLE_NAME>

示例:

DROP TABLE tableA
DROP TABLE test.tableB